My experience with PC freezing at random during gaming

For the past few months, I've had an issue where the PC will "freeze" at random intervals while gaming. It can sometimes take 2 hours to happen, it can sometimes take 20 minutes. The symptoms are always the same:
- The picture on the PC freezes
- The sound continues for 10 seconds, either playing normally, or looping the last half-second of sound
- The display then turns off, although the fans are still running and the HDD activity light keeps flashing at times

The only way I've found to resolve this is to press the reset button, there's no response to mouse, keyboard or power button.

Last night, I finally found the cause of my problem - the way my PSU was connected to my Crossfired 4870's. I'd initially discounted the PSU as a problem as it's a quality (if not top league) 880W unit that has been reviewed by several websites as reliable. Even with my set-up, 880W should be comfortably over the top for my PC so I thought it couldn't be the problem. I actually was clearing some boxes and found the pictoral instruction leaflet for the PSU. I noticed the illustration (for dual 8800Ultra's) showed line 1 from the PSU going into both 6-pin PCI-e power ports on card 1, and line 2 supplying both power ports on card 2. I had each line feeding a port on each card, as in my head this made the power demands balanced across the two lines.

It would appear the cards were taking most of their power from one of the ports, rather than taking an equal-ish amount from both. Because of the way I had the power cables connected, this meant one line was being asked to supply the power for both cards - and hence every now and again was shutting down. Now I've got each card on one dedicated line, I've had no more freezes at all.

My reason for posting this is simple - when I've been googling for an answer to my problems, I hadn't found any relevant answers for me. Hopefully by posting this on TomsHardware, someone else having the same issue with their Crossfire/SLI set up might stumble across this and save themselves some frustration. Or am I just the most stupid person in the world and nobody else would've set it up that way round?

Thanks for the suggestions Billin, but I've already solved my problem - I had the power connectors the wrong way round on my 4870 cards. I was posting this so that if anyone else has the same problem they might find my post and look for that themselves as nobody else mentioned it anywhere I could find.

I generally run 2x GPU-z, HWMonitor and Coretemp on my second screen while gaming and heat definitely wasn't the issue. I even manually set the fan speed to 50% in CCC to keep temps way down a few times - still froze. The freezing also occurred no matter which game I used in which of my 2 DVD drives, or even on my Steam games that don't use a disc at all.

Thanks for the suggestions, but my problem's already fixed - I'm just posting in the hope it might save someone else the 2 months of troubleshooting I've been trying.

Maybe, but impressively quick at offering advice and trying to help. Sorry if my reply came across as having a go, it wasn't meant to. Sincerely, thank you for trying to help.