XP allows for multiple user accounts with simple log off/on. If this is a problem then you can chance the other accounts by being logged into an admin account and going to start > control panel> user accounts and either changing or deleting the other accounts.

Windows sees partitions as drives and also your optics (CD/DVD) drives are also shown as such...

In my computer you should have :

c: drive (or local disc) this is the main windows drive.

then listed would be Drive A: floppy disk drive if your computer has one

Then listed the optical drives as CD or DVD or Ram drives.

in some configurations you may have
C: local disc and
D: as programs or windows
and E: as My documents or storage.

Also if there are any memory card readers ( for cameras) of flash (thumb) drives...these will also be seen as seperate drive.