JSI Tip 10198. USBDLM freeware allows you to specify the first available drive letter used when a removable drive is attached.

Download the USBDLM.zip file and unzip it.

The USBDLM.txt file contains:

USBDLM V1.x - USB Drive Letter Manager for Windows 2000 and XP

It's freeware for private and educational use. For use in a
commercial environment you need a license (after a test period).

See its homepage for more information and history:

Getting Started

When a removable drive (USB flash drive, card reader, harddisk) is
attached for the first time, Windows mounts it to the first free
drive letter. You can change the letter in the Windows Disk
Management Console with a lot of mouse clicks but you have to do
it again for every new device.

With USBDLM you can define a list of drive letters to use for new
removable drives.

USBDLM runs as Win32 service under Windows 2000 and XP.


Simply unzip the ZIP file into an empty folder.

Then enter your preferred drive letters into the USBDLM.INI.

If you are working with administrator privileges you can simply
start it.

USBDLM -install

Without administrator privileges you can start it thru 'runas':

runas /user:Administrator USBDLM -install

You can change the USBDLM.INI without restarting the service because
it's read each time a new drive gets the first free drive letter.

You can uninstall the service using parameter -uninstall:

USBDLM -uninstall

For a short test without installing the service you can start it with
parameter -debug:

USBDLM -debug

You will see a small empty window then. USBDLM stops when you close

To do all this out of the Windows Explorer I've made some command
_install.cmd, _uninstall.cmd, _start.cmd and _stop.cmd.

Defining the drive letters

The desired drive letters are defined in a USBDLM.INI file that looks


The just arrived drive will be un-mounted by USBDLM and afterwards newly
mounted to the first free of the defined letters.

The USBDLM.INI is searched on the new drive first. If there is none or
all there defined letters are taken the global USBDLM.INI is used (there
where the USBDLM.EXE is).
The latter one is used only if Windows mounted the new drive to the first
free letter. Otherwise Windows probably knew what it did...

You can name the USBDLM.INI on the removable drives with an underline in
front (_USBDLM.INI) to make it stays on top when the files are listed in
alphabetic order. The file can have the 'hidden' attribute.

Usually Windows remembers the last used mount points. So USBDLM will
intervene only when a drive appears for the first time or if its letter
was taken by another drive meanwhile and Windows gives the first free

If there is no media in the newly arrived drive (e.g. a Card Reader)
USBDLM stays idle. If you attach a multislot cardreader for the first time,
it's better to do it without a media in it. Otherwise USBDLM would become

I've made USBDLM for USB flash drives but in contrast to its name it handles
FireWire drives too.

These are the basic functions. See its homepage for more information and


USBDLM is freeware for private and educational use. For use in a commercial
environment you need a license (after a test period).

The software is NOT Public Domain software. You are allowed to freely distribute
of the software, but I retain ownership and copyright of the software.

You may distribute the software under the following conditions:

- You may not modify the program or documentation files in any way
- You must include all the files that were in the original distribution
- You may not reverse engineer the software
- You may not sell the software or charge a distribution fee, except to
  recover the media costs

The software and related documentation are provided "as is", without warranty
of any kind.

Uwe Sieber

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