You might want to try a System Restore to before the system was infected, and see if that works or not. If not, try running System File Checker (log on as an Admin, and run
sfc /scannow from the command prompt).
Another option is to do an
in-place upgrade (a repair install) of Windows.
When you're back online, I suggest scanning the system with Secunia's free
Personal Software Inspector to eliminate vulnerabilities that can leave the door open for the bad guys.