The thing about 2K/XP is that, unlike Windows 98 or ME where hard drives are assigned letters first, Windows XP and 2000 assign the next available drive letter to each device added, regardless of type.
Troubleshooting Info found here:
http://www.neoseeker.com/Hardware/faqs/kb/15,30.html
Troubleshooting
When you attempt to change an existing drive letter, you receive the following error message:
The volume volume_label drive_letter is currently in use.
If you continue, the new drive letter will be assigned; but you can still use the old drive letter to access the volume until you restart your computer. The old drive letter will not be available for assignment until you restart.
Warning: Changing the drive letter of a volume might cause programs to no longer run.
This error message can occur if there are files in use on the drive, partition, or volume. This includes files that are accessed by other people on the network. To resolve this behavior, use one of the following methods:
Click No when you receive the error message. Quit all programs that are using the files on the volume, and then change the drive letter (right-click the volume, click Change Drive Letter and Paths, and then click Change).
Click Yes to proceed with the drive letter change.
When you attempt to remove an existing drive letter, you receive the following error message:
The volume volume_label drive_letter is currently in use.
If you continue, the drive letter will be freed; however, it will still be available for use until you restart your computer.
Warning: Changing the drive letter of a volume might cause programs to no longer run.
This error message can occur if there are files in use on the drive, partition, or volume. This includes files that are accessed by other people on the network. To resolve this behavior, use one of the following methods:
Click No when you receive the error message. Quit all programs that are using the files on the volume, and then remove the drive letter (right-click the volume, click Change Drive Letter and Paths, and then click Remove).
Click Yes to remove the drive letter the next time you start your computer.
Hope this helps solve your problem.
Cactus