1. A computer can use up to 26 drive letters, from A through Z. 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), [Q307844].

2. When adding additional drives or a storage device that corresponds to a drive, XP automatically assigns the letter which may not be exactly what you want. However, the boot or system drive letter cannot be changed in this manner, [Q307844].

3. The article [Q307079] explains that by design, Disk Management may assign available drive letters to any unformatted hard disks/partitions on a computer and occurs so that you can issue a format command.

4. The article [Q830752] explains that if you have a universal serial bus (USB)-based CD-ROM drive attached to the computer, the CD-ROM drive may be mapped to more than one drive letter, and occurs if the patch described in the article has not been installed.