You are correct as to what the OP said. However, my point is that in most cases where that message is received the damage is more extensive and the disc will be needed. Since the installation is (presumed to be) licensed, the OP could borrow a disc.
OP: If this is Windows 7, you may be able to boot into a Repair Installation from the hidden 100MB partition. Press F8 when the picture of a window comes up and, if that works, choose a repair (or whatever it is, I don't have a Win7 machine handy to test and copy the text).
(Showing my ignorance, since I don't know if win7 has that file.)