I found this in windows help files...
To assign, change, or remove a drive letter
Using the Windows interface
Open Computer Management (Local).
In the console tree, click Disk Management.
Where?
Computer Management (Local)
Storage
Disk Management
Right-click a partition, logical drive, or volume, and then click Change Drive Letter and Paths.
Do one of the following:
To assign a drive letter, click Add, click the drive letter you want to use, and then click OK.
To modify a drive letter, click it, click Change, click the drive letter you want to use, and then click OK.
To remove a drive letter, click it, and then click Remove.
Important
Be careful when making drive-letter assignments because many MS-DOS and Windows programs make references to a specific drive letter. For example, the path environment variable shows specific drive letters in conjunction with program names.
Notes
To open Computer Management, click Start, and then click Control Panel. Double-click Administrative Tools, and then double-click Computer Management.
You must be logged on as an administrator or a member of the Administrators group in order to complete this procedure. If your computer is connected to a network, network policy settings might also prevent you from completing this procedure.
A computer can use up to 26 drive letters. Drive letters A and B are reserved for floppy disk drives, but you can assign these letters to removable drives if the computer does not have a floppy disk drive. Hard disk drives in the computer receive letters C through Z, while mapped network drives are assigned drive letters in reverse order (Z through B).
You cannot change the drive letter of the system volume or boot volume.
An error message may appear when you attempt to assign a letter to a volume, CD-ROM drive, or other removable media device, possibly because it is in use by a program in the system. If this happens, close the program accessing the volume or drive, and then click the Change Drive Letter and Paths command again.
Windows 2000 and Windows XP allow the static assignment of drive letters on volumes, partitions, and CD-ROM drives. This means that you permanently assign a drive letter to a specific partition, volume, or CD-ROM drive. When you add a new hard disk to an existing computer system, it will not affect statically assigned drive letters.
You can also mount a local drive at an empty folder on an NTFS volume using a drive path instead of a drive letter.
