Computer rebooting during games

Hi

I've been having some graphics card issues lately. Currently, the problem is my computer restarting randomly in the middle of playing a game.

Up until some weeks ago I was using my old X1950pro and it worked fine. Then one day my computer froze during playing a game, the sound looped for a while and the screen went blank. The computer seemed to remain powered though. This started happening more and more often. Soon I wasn't able to get any hardware accelerated graphics without the computer crashing immediately. Sometimes I didn't get a picture at all when booting. So, I tested the card in another computer, and the problems were the same. Ergo, broken graphics card.

I was able to borrow an X1550 from a friend until I got a new card. The X1550 worked alright, I had a few small problems with it but nothing big, no crashing or anything.

A week ago I went an bought an HD 4850. It has worked mostly ok, except that it sometimes crashes during games. It could take a few minutes, or might not happen at all. During the week I've had it, it has crashed 4 times. The games that have crashed it are TF2, L4D2 and GTAIV. What happens is that out of nowhere the screen goes black, the sound loops for less than a second and the computer restarts itself.

The thing that worries me here is that the symptoms are close to the ones I had with the X1950pro. So I started wondering, could the source of the problem be something other than the graphics card? Could my PSU for example be breaking the cards?

If the problem isn't caused by the graphics card, I'd guess it's either the motherboard or the PSU. It should be noted that the X1550 didn't cause any crashing, which could indicate that the mobo and PSU are fine. On the other hand, the X1550 didn't require a power cable -- X1950pro and HD 4850 do. Could the PSU be giving out incorrect voltages or something? Note that the other components have been working alright.

Other notes:
-I've tested the memory and didn't get any errors.
-I monitored the GPU temperature while playing GTAIV when it crashed and it only reached about 60C, so I don't think it's overheating.
-My PSU is 430W but I don't have a lot of stuff connected: HDD, DVD drive, disk drive, graphics card, rear fan, mobo.
-I found other people have had random crashing with the same card (albeit, mostly under different conditions) so it's not completely unheard of.
-I have the latest drivers for the card.

Any ideas what the problem could be and how I could diagnose it? One thing I can think of is to try another PSU but I'm not sure I can get one without buying. My main concern is that if the problem is not in the card, something in my computer could be breaking the cards, or does that sound unlikely?

My specs:
Asrock ConroeXFire-eSATA2
Intel E6300
2x1GB DDR2
XFX HD 4850
Antec Neo HE 430
Windows XP 32-bit

Any opinions, ideas and help appreciated.

I can't find the Neo HE 430 listed on Antec's American site but based on AMD's PSU recommendation for the Radeon 4850 your PSU could only barely power the beast XFX.
http://www.amd.com/us/products/des [...] ments.aspx

It would be an issue if like you stated the computer has to reboot when you stress the card in games, when that happens it's because your reliable Antec detects it's exceeding safe voltage and shuts down, that isn't good for your computer either as the hard drive can be writing something and a sudden power loss screws it up, the OS performs some maintenance task when you shut down properly so that won't happens either.

No opinion, I should ask does this happen in all games or just one in particular?

In my opinion GTA 4 is more CPU intensive than GPU, I still think you should upgrade the PSU to something with with a little more power. I would recommend anything on the that isn't rated at 430W.
http://www.newegg.com/Product/Prod [...] 20-%20500W