I upgraded from a nvidia 5200 to an ati radeon 9550. I experienced no crashes with my old video card, but the new one doesn't just freeze the computer, it restarts it. the screen will go black and the monitor click off. I've even tried it on a different motherboard(not for very long) and it worked fine. I have a chaintech mpm800-3 with a socket 478 celeron 2.93 ghz. i also receive a no conductor 80 cable installed line when booting but that's doesn't seem to cause any problems. any ideas?

If it works fine in another motherboard, then it's most likely incompatible. Does it only do that during games?

well, i didn't test extensively on the other mobo, but it really doesn't seem to like my current one. It only does in in games, but it doesn't crash all of them either. Some old ones like AoE 2 run just fine but some newer ones will crash before it gets to the menu.
What do you mean by incompatible?

DId you uninstall the Nvidia drivers before installing the new card?

how well cooled is your case....sounds like a heat issue with either the cpu or the vid card.....could you post your temps?

i uninstalled the old drivers first. I don't know the temps, but i do know the case and power supply are getting old. would running a game put a significant amount of stress on a power supply?

Newer games do tend to cause a newer card to demand more power from a power supply. Your psu could be marginal. What is the brand, wattage and amps on the +12V rail? If you open the case and look at the label on the power supply itself, it should tell you.

the power supply is an Enhance Electronics 300 watt. (i know, i shouldn't have just found a case lying around...)

Input: 115v/230v - 8a/4.5a
60hz/50hz

I don't think it's the psu that's causing problems. i also had thought it was the hard drive ( i had a very old one that was clicking) but i got a new one and it still dies on me.

do certain chipsets/processors work better with certain video card brands? my motherboard has a via chipset and an intel cpu.

I think it has been known to happen but generally it doesn't make any difference.

the psu is underpowered. Most systems will not run well with less than 400W.

you mentioned it only does it with certain games, well the older games dont ask too much from the video card which in turn doest stress out the psu that much
but a newer game will put the video card to work at its potential and thus puts a heavy load on a power supply that shouldnt be taking that much load

okay. thanks guys!

when buying a PSU add 30% to the cushion you already think you'll need. PSUs degrade over time. A 2 year old PSU running 24/7 will lose 30% efficiency due to capacitor aging.