Hi,

My computer keeps shutting down suddenly when i play any games on it and after it done this it needs powered off and then rebooted again before working. Im certain that this is not heat related that is causing the shut downs.

I did have this problem before and it was solved by going down a power supply (400 - 350) unfortunately i don't have the means to do that at the moment. That was when i was using and MX440 graphics card. I changed my card to a radeon 9600pro and i changed the power supply back to 400W and it was working properly. I then changed my graphics card to a 9600XT and these problems have resurfaced again.

Does anyone have any suggestions on getting my computer working properly again? Any help would be greatly appreciated.

Make sure the video card fully inserted, and try the latest drivers for the current card.

If no luck and previous cards are still listed in Dev. Mgr. and their software is still installed, then start in Safe mode, uninstall all video card software(incl. the current card), remove all video cards from Dev. Mgr., restart, let Windows recognize the current card, and reinstall its software.

If still no luck and you're using temperature sensor readings to determine that the CPU and system temps are ok, then it's still possible that the video card is overheating(this will not be indicated by a sensor).
First, make sure that the card's fan is running properly, and its heatsink and fan are securely and properly mounted.
If that's ok, then reduce the video card's acceleration and reduce the game's settings(resolution, color depth, etc.), and/or by remove the computer's cover and use an external fan to blow on the card.
If that works, then you may have to install add'l case fans. Recommended locations are lower front of the case(blowing in), and upper rear(blowing out).

If reducing the accel. and settings, and/or running the ext. fan does not work, then what make is the 400 watt PS, and what are your system's specs?