If you have important files that are stored in a particular disk drive disk partition that you don't want to expose it, you can hide it! Windows XP provides a utility to just that. Here is how it goes:
1. Go to Start > Run > Type diskpart
2. A dos window will appear (see below). Then type list volume.
3. So, if you want to hide drive C, then type select volume 2
4. Now type remove letter C (Note: Sometime it requires reboot.)
Diskpart will remove the letter. Windows XP is not having capabilty to identify the unkown volume.
Don't worry, your data will remains the same. Now if you want to unhide the drive, just repeat the process. But in 4th step, instead of typing "remove letter C", type "assign letter C"