If the data on the drive is not critical, I would avoid the "Repair Install" and perform a "Clean Install" that wipes the partition out, recreates it, reformats it, and then you should be good.... If your system is one that has the Restore on the D: partition of the same drive that it is trying to rebuld C: on and you dont have a System Restore CD or DVD set for the system, you will need to buy a new copy of the OS or Borrow a friends OS and activate your system against "YOUR KEY" affixed to your system, or it is ILLEGAL!!!