If you are overclocked, revert back to factory defaults.
Then, overclocked or not, try running the computer with only one stick of RAM. Then another stick if the first one doesn't work. (But only one at a time)
My laptop only has 1 stick of RAM. I tried taking it out and placed it back. Now, my laptop can't even start. And I mean CAN'T. The screen stays black even after I pressed the power on button.