Did you try file restore and it didnt work?
Use "run/execute". Type this while CD inserted. This will restore working copies of the system files.
If you have more than one partition, you could move the content of the desktop, my documents and whatever else of importance you have on the windows partition to another one (you can export your webbrowser bookmarks if need be, among others), before attempting a clean reinstall on top of the original wndows partition.