Restalling XP over existing install

Virus trashed the existing installation of XP Pro, it comes up to the wallpaper with no icons. All I can do is run items through the tast Manager’s File New Tast. Tryed to do an install over the existing installation to repair the installation using the original CD, but it’s XP SP1 and the system was updated to XP SP2 through updates off the update site. The system comes back to me and says that I cannot install over an older system. Do they give away XP Pro SP2 disks?
Is there a work around? Their web site is no help. If I do a fresh install by booting from the CD it will wipe all the settings.