I noticed my external drives, even when Time Machine was off, active at night when computer was asleep. ??? Anyway, in the morning, the video had died again, screen was black and wouldn't wake up. Already has replacement logic drive so NVDIA video card problem was not solved. How to I get to the System Log to see what actually happened? No error message when I restarted.

If your machine is truly hung this won't work, but have you tried screen sharing from your other computer?

I've just been trying to get it backed up so I can open a court case and get the computer replaced. I was curious if the external drives being active at night was 'normal' or if the problem with the Mac was doing it. Do they cron at night like the Mac does?

There might be all sorts of reasons why a drive is active even when the computer isn't doing anything. One common reason is that Spotlight is indexing the drive.