This software has been designed to list drive letter assignments to physical disk drives and hard disk partitions and to manipulate these assignments. Its main purpose is to restore drive letters when they get shifted after the installation of other hard disks, e.g. ones in hard disk racks. The drive letter changes, when made early enough upon the startup of DOS mode, are also visible in Windows 95/98/ME.

WARNING: It is important that all your DOS drives must have non-empty unique volume labels for this software to operate correctly!

NOTE: In this documentation, Windows means Windows 95/98/ME. In Windows NT/2000/XP, you can use the Disk Administrator, Disk Management or a similar utility of the Control Panel to assign drive letters anyway so this software is not needed.

CREDIT: Some ideas, data consistency checks and error messages in this software have been taken from the reverse engineering of DrvOrder (© by unknown, 2000).

1. Usage

Before using the software for the first time, see the next section for important notes!

The software comes in two flavors. You can use the executable version, with COM extension, of the software from the command line or AUTOEXEC.BAT:

DLMANIP [-|/<options>] <command> [<parameters>...]

Alternatively, you can use the driver version, with SYS extension, from CONFIG.SYS:

DEVICE=<path>\DLMANIP.SYS [-|/<options>] <command> [<parameters...>]

If parameters contain spaces, enclose them into quotation marks. In drive letters, you may append the colon, if you like.

If you install device drivers, from drives whose letter needs to be changed, in CONFIG.SYS then load the driver version of the software from CONFIG.SYS beforehands. Note that you have to specify the full name of the driver, including its path: at that point, the PATH environment variable is not defined yet so DOS cannot find the file automatically.

Note that the driver is not a real device driver: it does not install itself anywhere and it returns all the memory to DOS when it has finished processing the command specified.

Commands:

• LIST

  Lists the current drive letter assignments:

  <drive letter>Tab<partition name>Tab<volume label>Tab<serial number>

  The partition name follows a Linux-style naming convention (see below).

  The syntax for <serial number> is "####-####" where "#" represents a hexadecimal digit.

• SET <letter> <partition name> <volume label> <serial number>

  Moves the drive, that is situated on the specified partition and has the specified volume label and serial number, to <letter>. The letter of the original drive <letter> becomes undefined and is later replaced by the first available letter.

  The partition name follows a Linux-style naming convention (see below).

  The syntax for <serial number> is "####-####" where "#" represents a hexadecimal digit.

  Special values for <letter> are:

  -: Delete the drive letter. The drive will not be available anymore.

  *: Auto assign the drive letter. The drive will be assigned the first available letter.

  A special value for <partition name>, <volume label> and <serial number> is "*" which matches any partition, volume label or serial number: e.g. if you want to search for a volume label only, specify "*" for both the partition name and the serial number.

  To see the current settings of all drives, use the "LIST" command.

• MOVE <source letter> <destination letter>

  Moves the drive <source letter> to <destination letter>. The letter of the original drive <destination letter> becomes undefined and is later replaced by the first available letter.

• DELETE <letter>

  Deletes the drive <letter>. The drive will not be available anymore and its letter may be reused for other drives.

• SWAP <letter #1> <letter #2>

  Swaps the letters of two drives, <letter #1> and <letter #2>.

• REASSIGN <number of main hard disks>

  Reassigns letters, using the original DOS algorithm, to all drives.

  You have to specify the number of hard disks to which letters from the beginning of the alphabet are to be assigned. When all the partitions of this many hard disks got a letter, then and only then does the software advance to subsequent hard disks and assigns letters to their partitions, as well.

Options:

• Q: Makes the software operate quietly. Beware, in this mode, not even error messages are displayed!

The original DOS algorithm starts the assignment of hard disk partitions with the drive letter C:, independently of the number of floppy disk drives installed. It processes only those partitions whose type it recognizes – for DOS 3.x and above versions: FAT12 and FAT16; for DOS 7.x versions in Windows 95 OSR2 and Windows 98: FAT32, as well – and skips partitions of all other types – including but not limited to HPFS/NTFS, Linux native, Linux swap etc. Its main steps are the following:

1. Process the first primary partition of all hard disks.

   Start at first hard disk and see if it has a primary partition. If so, assign a drive letter to the first such primary partition (the one with the lowest partition number).

   Do the same with the next hard disk and continue until reaching the last hard disk.

2. Process all logical partitions of all hard disks.

   Start at first hard disk and see if it has an extended partition. (There may be one only extended partition, if any, on each hard disk). If so, traverse through it and assign subsequent drive letters to each logical drive, in the order that they are defined in the extended partition.

   Do the same with the next hard disk and continue until reaching the last hard disk.

3. Process further primary partitions of all hard disks.

   Start at first hard disk and see if it has more than one primary partition. If so, assign a drive letter to them, in the order of their definition in the Master Boot Record. Make sure to skip the first primary partition as a drive letter has already been assigned to it in step 1.

   Do the same with the next hard disk and continue until reaching the last hard disk.

Linux uses a significantly simpler algorithm. All partitions on all hard disks are processed, even if their type is not recognized. Its main steps are the following.

1. The two floppy disk drives are named "fd0" (usually A: under DOS/Windows) and "fd1" (usually B:). If more floppy disk drives are installed, they get subsequent numbers after the "fd" prefix.

2. IDE hard disks are named "hda", "hdb", "hdc" etc. Note that, unlike with DOS/Windows, these names do not change if other hard disks installed. The master hard disk on the primary IDE channel is always "hda"; the primary slave is always "hdb"; the secondary master is "hdc"; the secondary slave is "hdd" etc.

   SCSI hard disks are names "sda", "sdb", "sdc" etc., in a similar manner.

3. Primary and extended partitions, those defined in the Master Boot Record, are numbered from 1 to 4, thus are named "XdY1" to "XdY4" where "XdY" is the name assigned to their parent hard disk in step 2. (Yes, extended partitions also have a name, although they cannot be used to store data.)

4. If an extended partition exists, its logical drives are numbered from 5 upwards, in the order they were defined in the extended partition.

This software uses a similar algorithm for assigning names to partitions. The "LIST" command includes these partition names in its output:

1. The first device that the BIOS recognizes as an IDE hard disk, SCSI hard disk or equivalent is named "hda"; the second is named "hdb" etc.

   This device may also be an IDE/SCSI CD-ROM or DVD-ROM or a USB/Firewire hard disk, CD-ROM, DVD-ROM, flash drive or pen drive etc., if your BIOS supports accessing such devices – and can, perhaps, even boot from them.

   For this reason, unlike under Linux, "hda" is not necessarily the master hard disk on the primary IDE channel. Also, holes between IDE devices are not taken into account by the BIOS: e.g if the primary master is present, the primary slave is missing, and the secondary master is present then the secondary master will be named "hdb", not "hdc" as Linux would name it. This is a limitation of the BIOS, not this software.

2. Partitions are numbered the same way as under Linux (see above).

An example for drive letters shifting after the installation of another hard disk and the "REASSIGN" command taking care of it. You have two hard disks installed all the time, each have one primary partition and two logical drives. DOS assigns drive letters as the following:

C: First hard disk, primary partition
D: Second hard disk, primary partition
E: First hard disk, first logical drive
F: First hard disk, second logical drive
G: Second hard disk, first logical drive
H: Second hard disk, second logical drive

Now install a third hard disk, with one primary partition and two logical drives on it. The result is:

C: First hard disk, primary partition
D: Second hard disk, primary partition
E: Third hard disk, primary partition
F: First hard disk, first logical drive
G: First hard disk, second logical drive
H: Second hard disk, first logical drive
I: Second hard disk, second logical drive
J: Third hard disk, first logical drive
K: Third hard disk, second logical drive

As you can see, the logical drives of the two main hard disks had their letters shifted. Now use the "REASSIGN 2" command and you get:

C: First hard disk, primary partition
D: Second hard disk, primary partition
E: First hard disk, first logical drive
F: First hard disk, second logical drive
G: Second hard disk, first logical drive
H: Second hard disk, second logical drive
I: Third hard disk, primary partition
J: Third hard disk, first logical drive
K: Third hard disk, second logical drive

This is the original drive letter assignment plus letters from the end of the alphabet have been assigned to the partitions of the third hard disk. For a test, try the "REASSIGN 1" command, and you will get:

C: First hard disk, primary partition
D: First hard disk, first logical drive
E: First hard disk, second logical drive
F: Second hard disk, primary partition
G: Third hard disk, primary partition
H: Second hard disk, first logical drive
I: Second hard disk, second logical drive
J: Third hard disk, first logical drive
K: Third hard disk, second logical drive

Note that the letter D: is not assigned to the primary partition of the second hard disk anymore because you specified that you have only one main hard disk.

Drive letter manipulations also work under the DOS mode of Windows. If you launch Windows afterwards, the new drive letter assignments will be visible there, too.

Special note for Windows users! If your operating system is installed onto a partition whose drive letter has been changed, you may run into one or more of the following errors while Windows is being loaded:

• Symptom: Error message "Registry file was not found. Registry services may be inoperative for this session." displayed while loading. If you let Windows continue loading, the result will be a disaster: as no system configuration can be read from the registry, all settings fall back to default, similarly to safe mode or as if running Windows for the very first time, right after its installation.

  Reason: DOS mode seems to internally store the drive letter of the system partition, after having finished processing CONFIG.SYS so changing the drive letter in AUTOEXEC.BAT or from the command line is too late. The message means that the registry file has not been loaded because DOS could not find it.

  Solution: The drive letters have to be changed in CONFIG.SYS. You have to use the "DEVICE=" command in CONFIG.SYS to load the driver version of the software.

• Symptom: Error message "XMS cache problem. Registry services may be inoperative for this session." displayed while loading.

  Reason: DOS mode installs HIMEM.SYS, from the system partition, invisibly and automatically, before it starts processing CONFIG.SYS. The message means that HIMEM.SYS has not been loaded because DOS could not find it.

  Solution: Load HIMEM.SYS explicitly in CONFIG.SYS, using the correct path.

• Symptom: Loading aborts, fatal error "[VFAT Device Initialization Failed] A device or resource required by VFAT is not present or is unavailable. VFAT cannot continue loading. System halted." displayed on a blue screen.

  Reason: DOS mode installs IFSHLP.SYS, from the system partition, invisibly and automatically, before it starts processing CONFIG.SYS. The message means that IFSHLP.SYS has not been loaded because DOS could not find it.

  Solution: Load IFSHLP.SYS explicitly in CONFIG.SYS, using the correct path.

If your Windows ran fine before then these problems are, most probably, all related to DOS and Windows getting confused about the drive letter of the system partition being different from what it expects.

A suggested solution for all of the problems above is the following. First, copy the driver version of this software into a directory on a drive whose letter is never going to change – obviously, the best candidate for this is a directory on drive C: -; "C:\WINBOOT" in the example. Also copy HIMEM.SYS and IFSHLP.SYS from the Windows directory into this directory. Then prepend the following lines to your CONFIG.SYS:

DEVICE=C:\WINBOOT\DLMANIP.SYS /Q <command> <parameters...>
DEVICE=C:\WINBOOT\HIMEM.SYS
DEVICE=C:\WINBOOT\IFSHLP.SYS
[...]

The first line fixes drive letters. The second and third lines explicitly install the otherwise invisibly and automatically installed system drivers.

Use the letter manipulation commands of this software to change the drive letters, before letting DOS process the rest of CONFIG.SYS. Remember, these must be the first lines of your CONFIG.SYS!

If there are some other drivers that you install from the Windows directory in CONFIG.SYS then make a copy of those, too, and change your CONFIG.SYS accordingly. For example, to install country and code page settings:

[...]
COUNTRY=<country>,<code page>,C:\WINBOOT\COUNTRY.SYS
DEVICE=C:\WINBOOT\DISPLAY.SYS CON=(EGA,,1)
[...]

2. Important notes

• The software can only list and manipulate the drive letters of partitions that the underlying BIOS and DOS have already recognized upon booting up.

• The software refuses to work when a disk cache is present as drive letter changes may make the cache read/write data from/to the wrong drive. Changes are not permitted under Windows either, for similar reasons, only in DOS mode.

• Make sure to have unique volume labels and serial numbers for all your drives! Not only this software needs that but many others, too!

• Because the software deals with very delicate matters, make sure that it is the first software executed upon the boot process. If you use software that create drives (disk devices) – including but not limited to CD/DVD drives, SCSI drives, RAID drives, USB drives, Firewire drives, network drives, RAM disks, compressed drives, SUBST'ed, JOIN'ed, ASSIGN'ed drives – then change the drive letters with this software before loading the disk device drivers, otherwise those drivers may get confused.

• After any change, the "number of block devices installed" value is updated in a DOS internal table to the highest drive letter available at that moment. Otherwise, the directory structure of drives, whose letter is above this value, may not be completely visible: only the first file or directory in the root directory is returned. This is due to an intentional internal MS-DOS feature that is assumed to have been implemented to speed up access to disk drives.

  As a result of the update, the "number of block devices installed" value may be higher than the actual number of block devices, that is, disk drives installed and this may confuse some disk device drivers. Depending on the smartness of the disk device driver, you may or may not have problems with installing new drives to (unused) letters that are below the highest drive letter but above the "number of block devices installed" value. As a special case, after having moved a drive to the highest possible letter Z:, seeing the "number of block devices installed" value set to the equivalent of Z:, some (not so smart) device drivers may believe that there are no more drive letters available and refuse installation.

• Copying drive letters, that is, assigning multiple letters to the same drive is not possible as the result would be identical to the one above: only the first entry of the root directory is visible on the clone drives. Instead of this software, use the SUBST or ASSIGN commands of DOS.

• The DOS mode of Windows has serious problems with handling partitions that are very large (usually FAT32 partitions) and/or are beyond some BIOS hard disk size limit. As a result, the DOS mode recognizes the partition and assigns a letter to it but shows garbage instead of the partition contents or returns an error saying that the drive is invalid or unformatted.

  Beware, even if the partition contents seem to be fine, you may destroy data in other partitions if you write onto such strange drives! Your best choice is to delete them, with the "DELETE" command of this software, so that they are not available in DOS mode. When the Windows GUI boots up, it will recognize the partitions (again), assign letters to them (again) and handle their contents properly.

• You will get the "Drive letter beyond LASTDRIVE value" error if you try to move a drive to an unavailable letter. E.g. if your LASTDRIVE is set to G, you will not be able to use the letters H: to Z: for any drive.

  It is also important to know that while CONFIG.SYS is being processed, the LASTDRIVE value does not change. E.g. if you have altogether five DOS partitions on your hard disks, the device driver version of this software will see a LASTDRIVE value of G. Unfortunately, not even placing a "LASTDRIVE=Z" line before the call to the device driver helps with this: the LASTDRIVE value changes only after CONFIG.SYS has been processed completely.

  For this reason, you cannot move drives to letters at the end of the alphabet from CONFIG.SYS – in the example above, from H: to Z: –, this is possible only from AUTOEXEC.BAT, with the executable version of the software, after having raised the LASTDRIVE value in CONFIG.SYS. This is a limitation of DOS, not this software.

3. Error messages

• Unknown command

  You specified an unknown command.

• Invalid or missing parameter

  The syntax or the value of the parameter is invalid or too few parameters were specified on the command line.

• Drive letter beyond LASTDRIVE value

  The drive letter specified on the command line is higher than the highest drive letter currently available. See the important notes above for more information about the reason for this error.

• Unsupported DOS version

  You're using a DOS that is not supported. You need MS-DOS 4.0 or above. Also, the software refuses to work under most non-Microsoft DOS clones as their internal data areas may be different from Microsoft DOS'es.

• Windows running

  You are not allowed to manipulate drive letters when Windows is running. You should run the software before launching Windows.

• Cache detected

  You are not allowed to manipulate drive letters when a disk cache is installed. You should run the software before installing disk caches. Note that only SmartDrive and compatible disk caches are detected.

• Invalid LASTDRIVE value

  You need to set the "LASTDRIVE" parameter in CONFIG.SYS to a value of "D" or above. Also, a value of above "Z" probably means a damaged system area.

• Invalid DPB drivenum

  The logical drive number in a drive parameter block is beyond "Z". This probably means a non-compatible or damaged system area.

• CDS drive letter mismatch

  The first character – the drive letter – of the path in an entry of the current directory structure is not as expected. The drive is probably SUBST'ed. You should run the software before doing any other manipulations on logical drives.

• CDS or DPB chain corrupted

  The pointer to the drive parameter block of the same drive differs in the current directory structure and the chain of drive parameter blocks. This probably means a non-compatible or damaged system area.

• Invalid CDS structure

  The path in an entry of the current directory structures is neither "?:\..." nor "\\...". This probably means a non-compatible or damaged system area or some unusual disk device. You should run the software before installing custom disk devices.

4. History

0.10 beta (2003-06-29)

• First public release.

0.20 beta (2003-07-01)

• Fix: Added more updates so that, after the drive letter changes, the DOS system tables remain consistent. Without this, some software, that accesses the disk directly, refused to work.

• Fix: Made the "LIST" and "REASSIGN" commands work under MS-DOS versions 4.x to 6.x, as well, by getting the pointer to the drive table from a DOS service rather reading directly into the DOS system area.

• New: Created a device driver version of the software that can be run, before any other software, from CONFIG.SYS.

• New: Documented the method of changing the drive letter of the Windows system partition so that Windows can load successfully.

• New: Added the "/q" option to force quiet operation.

0.30 beta (2004-08-29)

• Mod: The "LIST" command outputs completely new data: Linux-style partition name, volume label and serial number.

• Mod: Refined the method of changing the drive letter of the Windows system partition: it is recommended to copy all drivers, that are needed upon startup, to drive C:.

• New: Added the "SET", "MOVE" and "DELETE" commands.

• New: Added important notes.

• New: Added BOOTREC.PAS, a proof-of-concept program that traverses through all partitions of all hard disks up to the 128 Gigabyte limit, reads the boot sectors of DOS partitions and displays their Linux-style partition name, volume label and serial number.

0.31 beta (2004-11-07)

• New: Added an important note about the impossibility of moving any drive, using the device driver version of the software from CONFIG.SYS, to a drive letter that is above the highest drive letter available upon booting.

0.32 beta (2004-11-28)

• New: A new error message "Drive letter beyond LASTDRIVE value" has been added.

• New: BOOTREC.EXE, the executable compiled from BOOTREC.PAS, is included.

0.33 beta (2005-05-08)

• Fix: Fixed a problem with detecting the end of DPB chains, that resulted in an "Invalid DPB drivenum" error in some cases.

0.35 beta (2013-03-16)

• New: Introducing support for FreeDOS.

• New: Several checks for whether drives are valid.

5. To do

The following changes are planned for the next release:

• Support for reading commands from a text file so that multiple drive letters can be changed via a single call.

• New command for writing the current drive letter assignments, as "SET" commands, into a text file that can later be used for restoring the assignments, without any manual editing.

• Wildcards and intervals for the "SET" command so that the letters of multiple drives, with similar volume labels and/or serial numbers, can be changed in a single command.

6. Copyright and legal issues

This software is freeware. You may use it as long as you wish and you may spread it as you like provided that it is in the original unmodified archive. Don't distribute single files, only the whole package, and don't ask for money above the normal fee of the distribution media itself. This software may not be included in any compilation, sold on disk or CD/DVD-ROM or bundled with software or hardware without prior permission from the author.

The source of this software is public domain and provided here "as is" – I don't feel like commenting it more but if you have problems then feel free to ask me. If you derive your own software from the source or put a part of the source into your own software, please, give me a credit and send a copy to me.

The author accepts no liability for any damage or data loss caused by this software.

7. The author

If you're interested in some similarly useful utilities then contact me at the E-mail address sta@c64.org or visit my homepage at http://sta.c64.org.

Joe Forster/STA
17th March, 2013