You can do it from inside Windows XP by simply right clicking on the drive and selecting format, and then making sure it's in the NTFS option. If that doesn't work for ya, you can use the Windows XP CD to do it as well, but make sure you choose the right drive if you do it that way.
Just boot into the CD like you're gonna format the drive and install Windows. The easiest way is definitely from within Windows like Thunder and sailor said.
-Lasereth