After you boot off of your WinXP CD, and it loads all the crap that it needs. It will eventually show you a table with the hard drives that are in your computer, asking you where to install the XP files. At this screen there is an option at the bottom of the screen either "D" or "L" I think it is to Delete Partition. select the drive you want to format, and delete the partion(s) off of it using the "D" or "L" key as directed by your computer. Then once you have the partitions deleted, it will show your hard drive as "unallocated space" Select the unallocated space, and there will be an option to "Create new partition", create a new primary partition, and select your formatting option (I ussually do the low level format NOT the quick option, but you can use either depending on your needs). Once the format is complete, you should have a blank hard drive, ready to reinstall Windows again, or whatever you wanted to do with your formatted hard drive.