HP drivers for a dell machine? I dunno a great deal about Dells as I've never owned one but are those the ones it tells you to get ont he Dell site, as I would have thought they'd have their own?

As for XP, you need to go into the setup BEFORE booting, usually thru hitting delete, and set your boot device to CD. Then you should get onto the setup menu and be able to choose to delete the partitions