Sudden reboots immediately when I plan a new complex game

[plex4r]

My homebuilt runs fine under all conditions except for advanced gaming when it halts and suddenly reboots. (Games like Half-Life2, Age of Titans).
I have updated all of the drivers with no effect. Temp's are good, I have 4 sensors that all read OK.
I suspect it may be power related. Does anyone have any advice on how to diagnose? If it is power, how can I test this, get a new one?

Here are the components:
Thermaltake Lanfire Xaser III, that came with a Silent Purepower power suppply at 450 Watts (I think, but I know it was enough for my components)
AMD 64 3500 CPU
ASUS A8V motherboard
ATI 9800 AIW video card.


Thanks, plex4r

 

[pickxx]

your PSU should be enough but if its dieing then it wont be....

look in your BIOS for your voltages on your rails....write them down and post them. Also yuo will need to max out your computers power and put everything to 100% and know those V's too....

 

[Rugger]

Have you googled the error from the BSOD? If you're not getting the BSOD, then cancel the auto reboot on error in Windows settings.

 

[PluggedN]

Yea I agree that the psu should be sufficient however this does sound like a power issue. Monitor your rails under load and see how badly they dip.