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Reassigning drive letters automatically


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Here is the batch description:

:: -------------------------------------------------------------------------------

:: MapDrive.cmd: Assign letters to Drives

:: ------------

:: Purpose: Automatic assignement of new letter to drives without reboot.


:: Parameters:

:: ----------

::    1. Language ID (ENU, FRA, DEU, NLD,...).  No default value, mandatory.

::    2. TEST to do everything except the drives de/re-assignment.  The log file

::        TMP_MAPDRIVE_date_time.LOG is created: you can display it to see the expected assignments.

::        The environment variables TMP_VOLDESC- show the assignments to be done.

::    3. TempPath : Path where temporary files will be created.  Default is current directory.

::        Path could be enclosed in quotes and could terminated by a backslsh.

::        This is the 2d parameter if the 1st one (TEST) is omitted.


:: Why this program?

:: ----------------

::    Because during unattended Windows installation, I didn't want to reassign

::    manually my drives (S: for Save, W: for my CD Writer, V: for my DVD, T: for

::    temporary data, U: for backups, G: for games,...)


:: How to use it?

:: -------------

::    1. Create a file DRIVE.x on each drive to be reassigned as x:.

::    2. On the system drive, create a file CDR.x where x is the letter to assign

::        the the CD reader[/writer].  For unattended installation, create this file

::        in $OEM$\$1\.

::    3. In the same way, create a file DVD.x for the DVD reader[/writer] on the system drive.

::    4. On the system drive, create a DRIVE-.x for each letter x that you don't want

::        to be assigned (= reserved letters for USB Key,...).

::    5. For unattended Windows installation, (FRA for French,...)

::            add these lines in the file RunOnceEx.cmd

::                (they should be modified according to your situation):

::                SET KEY=HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\RunOnceEx

::                REG ADD %KEY%\001 /VE  /D "Modifying Drives Letters" /f

::                REG ADD %KEY%\001 /V 1 /D "%SystemDrive%\Install\MapDrive.cmd FRA >%SystemDrive%\MapDrive.log 2>&1" /f

::            or add one of these lines in CMDLINES.TXT (under [COMMANDS]):

::                "MapDrive.cmd FRA %SystemDrive%\Temp >%SystemDrive%\Temp"

::                "MapDrive.cmd FRA TEST %SystemDrive%\Temp >%SystemDrive%\Temp"


:: Before running:

:: --------------

::  - If your windows language is not in the language ID set (see above in the "Parameters", 1.),

::    you should have the correct value in the environment string STR2FIND.

::    To do that, you should put a part of the answer DISKPART display when you

::    try to modify a reassignable drive letter.

::    To find this string, execute the following (without the text in () which are comments):

::        DISKPART

::        LIST VOLUME

::        SELECT VOLUME x (select an n on-system drive)

::        ASSIGN LETTER d (the same as the current letter)

::                        (DISPART display the message that you should take)

::        SELECT VOLUME y (select the system drive)

::        ASSIGN LETTER e (the same as the current letter of the system drive)

::                        (DISPART display an error message telling you that you

::                        ( cannot reassign the letter for a system drive, boot

::                        ( drive or a drive qhere is the swap file)

::        EXIT

::    You should take a part of the first message which is not in the second

::    message, and stop the string on accentuated characters.


:: Notes:

:: -----

:: When run, MapDrive.cmd scans all the drives (volumes) for files matching

::    "\DRIVE.?".  If the file "\DRIVE.d" is encountered on a volume, this volume

::    is reassigned with the letter "d:".

:: Do not forget that the system drive as well as the drive containing the page

::    file (and others) could not be reassigned.

:: You may also reassign CD/DVD letters by creating one or many files "\DVD.d"

::    and/or "\CDR.d" on the system drive.

:: You may also disable drive letters by creating one or many files "\DRIVE-.d"

::    on the system drive.


:: This script works on FAT32 and NTFS file system.  this is not the case for

::    MOUNTVOL which accepts only NTFS.  Furthermore, no reboot is required.


:: The drives which are already assigned to the "good" letter will not be removed

::    nor reassigned.


:: IMPORTANT:  I am not responsible for any damage caused directly or indirectly

::    by this program.  So, before using it, run this batch with TEST as second parameter.

:: -------------------------------------------------------------------------------

EDIT: If your Windows language is English, German, Dutch or French, you don't have to worry about all of that: just call

MapDrive ENU, or MapDrive DEU, MapDrive NLD or MapDrive FRA.


Current attachement version is 2008/08/04:

:: 2008/08/04 : Dutch language added (Thanks to Orcinus)

:: 2005/10/30 : Reassigning twice (to avoid bad assigning to a used letter)

:: 2005/10/28 : Try to keep the existing letters.

:: Group deasignments and reassignments.


Keywords: drive drives partition partitions letter letters volume volumes mapdrive drivemap diskpart change changing rename renaming modify modifying



Edited by mdes
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Good job, i quickly read the script and i understand how it works. I will test it next time.

But for non french version, there is a problem

Line 99 you use --> FIND /C "La lettre sp"

The string is in french so in other language version, the string won't be find.


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But for non french version, there is a problem

Line 99 you use -->  FIND /C "La lettre sp"

The string is in french so in other language version, the string won't be find.

You are right :) I added comment in the post and in the batch file to tell how to change this string.

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now honestly, is it reliable? :rolleyes:

Yes it has been tested :D

The only problem I encountered is that, sometimes (it depends of the installed Windows), the CD drive is not reassigned when there is a CD in the tray. I found why: the output file of DISKPART is UNICODE, so there is 2 characters at the file beginning. I will solve this problem in a few hours :)

EDIT: Sould be solved now: This was not a UNICODE problem but LF instead of CRLF.

Edited by mdes
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I've tried running this on a Ghost 8 PC-dos boot disk (floppy) to boot to a lan mount of the Install/Windist dir,

it no worky fo me

I get this spew about

"Out of environment space"

"Bad command or filename"

can someone explain how to run this mapdrive.cmd on an unattended install

(obviously prior to install so my D and E are in the right place)

I'm trying to accomplish this on a dual boot (xp/2K) machine :)

(2 C:'s (each hidden from each other), 2 D:'s, and 1 E:)

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Yes, MapDrive.cmd use a lot a environment space :) Here is a solution:

In CONFIG.SYS, add the following line

shell=C:\cmd.com /P /E:nnn

where n is the number of bytes you want to set aside for the environment. For DOS 6.22 nnn represents the number of bytes you want to set aside. So for a 2K environment take nnn=2048 (try with a larger value, e.g. 8192 or more)

About ""Bad command or filename", I suppose this is a consequence of the out of environement space.

For unattended, I am using the following:

File command.txt


File RunOnceEx.cmd

SET KEY=HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\RunOnceEx...REG ADD %KEY%\800 /VE  /D "Modifying Drives Letters" /fREG ADD %KEY%\800 /V 1 /D "%systemdrive%\Install\MapDrive.cmd" /f...
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shell=C:\cmd.com /P /E:nnn

Thanks eh! :)

saw that on one of my anicent config.sys's, was wondering what that was lol

question: is that ram or cache and how far could you go with say:

256K cache=?

512K cache=?

256Meg Ram=?

1024Meg Ram=?

File RunOnceEx.cmd

Didn't know it could be run that late in the game eh. Awesome :rolleyes:

(but before anything else of course)

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k not getting any environment errors,

(although 8192 might be a little high; and it stopped NET.exe from from doing something, I still got in.)

but still getting syntax erros and bad command or filename

(repeated about 20-30 times)

just tried running diskpart

says it cannot be run under dos

so i guess its the runonceex method eh

question about that then,

Won't I need it to run before the os even gets installed so that my folder redirections will work?



or is the 12/13minute mark going to be ok for that?

(runonceex launched from/in commandlines.txt) or is it going to have to be put someplace sooner?

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doh! n/m just stuck it 2nd in the list. :)

REG ADD %KEY%\001 /VE /D "Turning system restore off" /fREG ADD %KEY%\001 /V 1 /D "REGEDIT /S Z:\SCRIPTS\sysresoff.reg" /f
REG ADD %KEY%\002 /VE  /D "Modifying Drives Letters" /fREG ADD %KEY%\002 /V 1 /D "Z:\SCRIPTS\MapDrive.cmd" /f
REG ADD %KEY%\003 /VE /D "Setting Personal & Settings Folders Redirects" /fREG ADD %KEY%\003 /V 1 /D "REGEDIT /S Z:\SCRIPTS\Redirect.inf" /f

that should do it eh :rolleyes:

but i'm still stuck on this tho :D


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