I know that you installed a new drive, but your problem sound so similar to my buddy's problem. Take the compute to someone else's place, no problems. Back at home, it didn't want to run right. Coud be a loose cable on the drive or motherboard? He also mention that he had electric problem at his place.
The odds that it's the drive is pretty high, but it could be? And you did replace the drive once before.
Here's the latest experiment: swapped out the power outlets and power bar to a different room. No change. Swapped out the keyboard and mouse: I can work.What puzzles me about this is I haven't had trouble with the keyboard. The mouse seemed to work fine as well.