How will that other person by accessing the drive? Locally or over a
network?
You could use permissions if using NTFS in XP and NTFS on the shared drive.
NOTE: Recommend sharing and setting permissions on a folder basis rather
than a drive basis.
If you want to lock down the drive with password protection, you'll need
third party software. I don't know of any programs that lock a whole drive
but there are programs that lock folders. A google search should turn up a
few.