Right here's the deal, my computer is about three months old. Two days ago I downloaded Steam with L4D then I played it. It worked fine for the first night then this happened.
Half way through a game my monitor went black, displayed no signal, continues loop of the last note of sound but the weird thing is my computer stayed on. So I can only think that this is not a overheating issue as the computer would of just cut out right?
My rig: Intel Core i3 2120, Asus P8H61, 8GB Corsair 1600mhz Vengeance, AMD Radeon HD 7770 1GB and a 600W Xigmatek.
Not the best of rig but should be able to run this game no problem, which it did for the first night.
I had a look over the temps and here are my results through Hardware Monitor, take note Hardware Monitor has a glitch with Asus motherboards that's why it says my CPU is running at 87 degrees, I know this for sure cause I can still touch it without my hands being burnt off, but here's the results:
More about :crashing sound looping monitor turning
Even if your power supply passes the paper-clip test that Panicmaster links to, I would still suspect it. I had very similar symptoms a while back and the cause was my graphics card not getting the required power from the power supply. I replaced my 450 watt Cooler Master power supply with a 500 watt Antec and my problems disappeared. However, I would probably invest in a power supply tester before scrapping your current PSU.
The key for me from the OPs post, is the sound looping. When I was having my issues, my screen would either lock with the last image, lock completely garbled, or go completely black. Regardless of what the screen did, the sound was always looping.