Originally Posted by notabook

No, you do not have to format. From XP type the following:
Click start, go to All Programs, go to Accessories then click Command Prompt (alternatively click start/run/type cmd, press enter).

In the command prompt screen, type the following: convert drive_letter: /fs:ntfs
EXAMPLE: convert C: /fs:ntfs

Make sure any important data is backed up just in case blah blah blah.