random pc restarts

hopefully i can get some help here. my computer has been randomly restarting itself. it had originally came with a msi board in it and i thought the board had gone bad. when i would play games, do video editing, or even stream audio it would just restart without any clue as to why. so i figured the board was bad, upgraded to an asus board and new cpu/heatsink.

thinking this was the end of the problem, i started to play wow and i got the same problem. although it happens less frequently now, its still rather annoying because i spent the money on a new board and it didn't fix the problem. now it only occurs when i'm playing a game as i can leave the computer on all day with no problems. i'll leave a window open on the screen to test this and have had no problems for 3 days in a row but the moment i play a game, restart about 10-30mintues into it.

so i'm thinking it has got to be the graphics card now or the psu. i believe i got an ati 1300 pro in there (don't remember). i do remember when playing games, there would be a fan that kicks on every few mintues really high to cool the card. now that i think about it, i dont remember recently hearing that fan noise as it shuts down me and i just go to my laptop to play games.

in looking around the net, i seen a few posts saying that a bad psu will randomly restart. this is why i think it could be the psu as it is the stock psu from abs at 300watt i think. so i figure with an added hard drive, dvd burner, memory, and dedicated graphics card, it's been too much for the psu and now its starting to go bad.

just wondering what someone here might think or suggest as i'm kind of at weird spot as to what to buy, new graphics card or psu.

thanks

and what is your CPU temps at? If it's something like 50C at idle... then that's most likely the problem... You did remember to pull off that plastic film off the heatsink heatpad, right? or used artic silver, and only a drop of the stuff, not the whole tube....

And yeah a broken PSU will cause reboots like that.... but, so will a number of other things....

oh i've wiped the hard drive clean multiple times thinking it was the os. tired vista, and xp, even me. multiple virus scans show nothing either. i tried opening the case yesterday afternoon and checked out the fans, they are all running, even on the graphics card. since it was cold in the house, i left the case open and ran a game on it to see if the cold air would have effect on keeping temps down. there was not one incident of a reboot during the entire time i spent playing the game. i'm just going to bite the bullet and replace the psu first to see if that is the cause. if its still happening, i'll go and change out the graphics card.

my thinking now is the psu. although the fan was spinning, there wasn't a whole lot of airflow moving out of it. i'm going to try blowing air through it and clear any dust build up that might be blocking flows.

i've used artic silver, cleaned off the heatsink surface really well. it was also happening before with the original mb and cpu.

thanks everyone for their comments.

Umm... huh?

You opened the case up and played a game and it didn't reboot once.... and believe the PSU was the cause? Where did that idea come from?

My logic says it's overheating.... That your case has no airflow, may be too small, or the wires inside need to be better organized to allow for better airflow. (BTW: you never stated what temp. that CPU was running at...)

do you have catalyst control center installed?

thats what used to happen to me with my x800 when ccc was installed, i would play a game for 10-30 minutes and my computer would restart.

i just uninstalled it and everything ran fine.