Hopefully you at least have a recovery disk or full installation disk onhand. You may have to wipe the hard drive by allowing the XP installer to delete the current partition after deletion of the current infected installation to simply wipe the drive without wiping out Dell's own hidden partition for the reinstallation of Windows. You would do that if you have already run a few different virus removers and feel that something else could still be on the drive. Here's a free edition of Grisoft's AVG 7.1 you can try before wiping the drive entirely.
http://free.grisoft.com/doc/2/lng/us/tpl/v5
For added protection after a clean install and to see what adwares/spywares can be found and removed these two links may help.
http://www.lavasoft.com
http://www.microsoft.com/athome/secu...e/default.mspx