do a fresh install of windows. that way youll wipe everything off your hard drive in the setup and youll have a nice clean installation to play with
that should bee what you need to do. ...just did a fresh reinstall of windows xp this morning on my dell, had to put the disk in restart and press f12 when the dell logo came up to choose to boot from my cd rom. finished installing all the driver and sp2 this evening, didn't have to put all the crap that usually comes on a new computer (such as AOL, earthlink, norton AND mcafee, etc...), wow what a difference it makes, my computer runs so much better now!
All you do is put the windows disc in your cd drive... thats it if the bios is set to boot from the cd drive first then setup will automatically start (or say press any key to boot from cd) then just follow the install wizard... easy
loading windows and formatting was really easy, i had to load a lot of the drivers seperately though and that can be a pain... other than that, it went great!