Overclocking is always a risky business. The odds of damaging the processor or other components, such as the memory, are very high if you don't know exactly what you're doing. It may be possible to take the hard drive out of the system, boot it on another computer, and determine the error message there -- although the "Corrupt or missing" file problem is not always a sign of a corrupt or missing file. It's sometimes also a memory parity error, which leads me to think it may be possible that the overclock settings may have damaged the system's memory.
This was first published in March 2004