Dell's computers usually come with a restore CD, which restores the hard disk back to its factory configurations. That means you might want to do backup copies of everything you currently have. Try to have a copy of any driver software of any hardware you might have installed. After you restore the hard disk - and I'm not so sure how efficient those Dell CDs are, as I have never used them - you might want to re-do all the windows updates patches (which might take quite a while).