Starting Up - Black Screen - Machine_check_exception STOP OV000009c

When I start up, I get the blue windows screen saying it needs to "check file and folders," but at the bottom of the screen where it gives the percentage scanned, it stays at zero, and after a couple of minutes, goes to a black screen and and says "machine_check_exception STOP:OV000009c,."whatever that means. If I hit anything on the keyboard (on the first screen) before it attempts to scan, it starts up fine, and runs fine. I tried defrag and doing the "correct error" thing from the Properties tab in My Computer C Drive. I used to get this if the computer was not shut down properly, but it would scan up to 100%. Now it does nothing. how to correct this, or should I expect the whole thing to crash if I keep using it this way?