I have been having problems with my computer for a while. It seems that every time I want to play a game, my computer thinks that 15 minutes into the game, restarting is a good idea. Anyway, I did hours if research checking what could be the possible problem. People told me this:

Could be Windows/Software probelms
Could be Memory problems
Could be Overheating problems
Could be Power Supply problems

So what I did first was re-formatted my hard drive and re-installed windows and all that. After, I still had the same problem, so I X'd "windows/software problems" off my list.
Next I found a handy dandy program named MemTest86 and I tested my memory. First with only one chip in, then with the other, and then with both. I only encountered one error when both were plugged in, and i'm pretty sure it was because I had the second stick plugged into the wrong port. I swithed the second one into the other available memory slot, and then did another memtest, and no errors occured.
I have had heating probelsm before with old CPU's (specifically my old T-Bird 1.4) so I knew what the possible outcome could be (my motherboard and processor melting together). Since i'm running on a Asus A7N8X-Deluxe I decided I would use the AsusProbe tool to keep a check on the heat. I used the recording tool while I played games and waited for a restart. Once I was back in windows, I checked the Probe log, and the CPU/MB temps never reached a dangerous height.
So this leaves me with the power supply. But I just want to make sure that's what's wrong before I spend money replacing it. 60$ for a new PSU might not be a lot for some people, but i'm a very very broke person right now. Anyway. AsusProbe tells me that my power is fluxuating like crazy. it looks something like this:

+12v goes between 12.416 and 12.352
+5v goes between 4.865 and 4.73
3.3v goes between 3.056 and 3.376
vcore goes between 1.696 and 1.712

I don't know too much about voltages, but something tells me that the 3.3v should not be dropping that low. And it also worries me that the +5v is always lower than 5. The default settings on AsusProbe tell me that the voltages are fine as long as they are +/- 10%, but many other websites I have visited tell me that anything out of the +/- 5% range is bad.

Is there any other way I can check if it's the power supply failing without having to buy a new one, or borrow one for a friend to test with?

Thanks for your time.

You can get a new power supply for less than 25 bucks online... other than that you can get a power supply tester online also. Check tigerdirect.com for both.

How big is your PSU?

If this only happens with games I would suspect overheating of either the CPU or the GPU (graphics chip). Are you monitoring system and processor temperatures? That is the place to start before rushing off to buy a PSU.

First off (mac4_life) - I know I can get a new PSU for about 25$, but I since that's what I did last 2 times and they failed one me, I think i'm going to buy one that is more expensive and more reliable.

Second (OtheHill) - The problem also happens when I am doing other things that require lots of processing. Today I was converting a .avi into a DVD image, browsing the internet, and listening to music at the same time and I got a restart. AsusProbe tells me that my CPU temp is usually around 56c and the default threshold is 72c. PLus I have ready that temps up to 75c on a 2400+ are acceptable.
Also - Is there software that I can use to monitor the temp of my GPU, because i've noticed that there is no fan on the GPU of my video card (radeon 9600) and the card I had years before that had a fan (GeForce 3 original). And usually as processors get faster/better, they require better cooling. And my new card is generations past my old one, yet still has no fan.

IMO 75c isn't acceptable temp. When and how are you obtaining the CPU temps? If you are rebooting to the BIOS and looking there the temps can fall off quite fast. The Graphics card/chip can cause the symptoms you have if it is overheating. Defective memory can also cause problems. Your problem may well be the PSU but I would check the other things first. Run a memory test on your memory and monitor the temps when the computer is being stressed.

Re: OtheHill

In my first post I mentioned that I use AsusProbe to watch my CPU/MB temp. When under a lot of stress, it warms up to 56(cpu)/32(mb)
I also mentioned in my first post that I tried memtest86 with my memory. First with one of the chips, then with the other, then with both. I also tried other variations in other slots, and the only time I got errors was if I put a ram chip in the wrong memory slot (ie: putting memory in slots 1 and 3, but not 2).