Realizing the word "CPU" to be the cabinet,I strongly doubt that's your RAM.Maybe it's gone faulty. Or most probably the RAM has got loose from its slot. I mean partially removed. So you should open your case,take out the RAM from its slot,and re-insert it into the slot properly. If my assumption is right,this should work,and your system should boot up fine. If it doesn't,you'll have to troubleshoot the issue further. Keep me posted friend.