you can repair windows, problem is it's a Major Pain. use a boot disk to replace four initialization files, boot.ini, ntdlr, then I guess you could use an old registry, if you have backups. then on a working system (or from internet data) see what the virus altered, and use the recovery console to repair the damages. i've seen this done quite a few times, but it's not something i'd want to do, storage is cheap now, and you can backup with gigabit ethernet, no need to worry really.