I don't know if it works the same on a Dell, but you should need to hit delete on startup to get into the BIOS, tell it to boot from the CD-ROM first. Have your Win XP disc in the drive when you restart after saving the settings. It will let you format somewhere in there. Additionally, you can probably set up some partitions if you want, so that the next time it gets screwed up, you just need to format the OS partition.