hi, welcome to DAL,
This is just a possibility but is better than a clean install, it just re-installs the windows files and leaves everything else alone:
http://www.michaelstevenstech.com/XP...install.htm#RI
I would recommend backing up important data to another HD (not the "C:" drive as this is the one with the windows files in it) or CD/DVD.
I have used this a number of times and once, it completed and restarted to a blue screen leaving me only the option to do a clean install.
there may be a simpler solution for this but i dont know what it is.
Hope this helps,
Mike