[kirab]

Hey all, I built my PC about 5 or 6 months ago and everything has been running fine until recently. The specs are:

AMD 64 3000+
1GB DDR RAM
ATI Radeon X800 Pro
80GB HDD
430W PSU (Thermaltake TR2 - ATX 12V 1.3)

Problem is, when I'm in the middle of doing something, the PC just shuts itself off. This has happened during MapleStory (a very low-intense game) and Splinter Cell (the first one). I thought this was temperature related but I checked temps while I was running Guild Wars (more computer-intensive than any of the two above games) and they were all fine (i.e. from 30 - 55 celsius).

Any suggestions?

[joiner59]

Check to see if the back of your Motherboard isnt touching the case.

[MrCoffee]

Could be a failing PSU, try swaping it for a spare or testing it with a voltmeter under load.
Run prime95 and look at your cpu temps at the same time, if you hit 55-60+ then you're probably overheating.

Run full virus/spyware scans.

[CrazeD]

Have you tried different RAM?

[MrCoffee]

Good point, run Memtest86 as well, though I'd expect a BSOD if you have faulty ram.

[wasisnt]

It could be RAM, motherboard, CPU, power supply etc. It may take a little troublshooting to figure it out.

[jeremy]

i highly doubt its the ram , bad/unstable ram will never make the pc shutdown by itself , it can only cause file curruption/random restarts/bsods ,and very unlikely the cpu itself maybe you meant overheating

download sandra click here get into hardware-->mainboard , scroll down til youll see temperature/voltage sensors & take a screenshot

check the mobo for bad capacitors and better use a flashlight cuz its kinda dark in there , see examples
http://home.earthlink.net/~doniteli/index27.htm
http://www.pcstats.com/articleview.cfm?articleID=195

[Jby]

Can you please clarify what you mean by shutting down?
Is the power cut completely and any keyboard/mice lights go out, or does it just interrupt with a windows "shutting down" screen, or do you get a BSOD?

I doubt it is memory if you're not getting a BSOD, memory errors as mentioned above will always (I think) produce a BSOD or an automatic restart.

If the power is completely cut then its most likely a problem with the PSU, is there a light on your motherboard and is it lit when the computer shuts down?

If the computer goes through the formal "windows is shutting down" procedure then it's likely a virus, even though its hard to tell from your description I don't think this is the case.

It seems to only be happening at times of high load i.e. when you are running games.
Try installing something like ASUS PCProbe which allows you to monitor fan speeds, voltages to CPU and other devices and temperatures, look for anything unusual.

If you can get your hands on a mulitmeter and check the rails then do so to make sure it is your PSU before replacing anything.

[kirab]

Can you please clarify what you mean by shutting down?

The computer just turns off. I would be doing something and then the power light on the computer goes dead. There's no "Windows is shutting down..." etc.

I haven't tried different RAM (don't have any more) but the temps seem fine according to everest. I'll get back to you guys with more info.

Will upload temp/voltage pic soon.

[MrCoffee]

PSU is a prime candidate then, are you positive you have all the power connectors plugged in? I have seen motherboards with as many as 4 different power connectors.
I'm guessing you have a 20/24 ATX connector and an additional 4 pin connector.

With sandra use 2005 lite, environment monitor and run something like prime95 along side, make sure the voltages etc. are stable and within tolerance 5-10%