been there!!

You'll need to find several things. First is a disk wipe software program - usually takes a good while to wipe a drive and all the boot and MBR stuff. Check out tucows.com for it. Or if you have a Ubuntu OS disk - load it and do the disk wipe/partitioning or prep to install the OS but quite before the actual OS installs.

Once that is done be sure to have all the drivers for the XP use on this PC. If you don't windows may be there but will not operate correctly and will prompt you for the proper drivers for the mother board.

Go to the manufacture site and read up if they have the XP drives for the rebuild. Else you may be stuck with the Vista OS - BEEN THERE! And that sucks! The way around that is to go to the Win 7 OS an maybe the business version for the XP duality.

Do the homework!