VL, if you ONLY reinstall windows without formatting the drive it SHOULD only overwrite the windows directory (find a way to move "documents and settings, just to make sure). You'll have to reinstall some things, but you should keep all your "important stuff".
But don't jump straight to that solution, try the "repair" option from an XP CD. That will only touch the actual OS side of things and leave everything else alone. You will have to do every windows update again, no doubt reinstall some drivers, etc, as Windows will be put "back" to the same state as it was when the disk was poduced (probably pre-SP2, etc) but the rest of your data will be safe.
And please remember to back things up.