Need help with a strange problem with my Dimension 8400

So my Dell is out of warranty and I cant get any help on the Dell support forums. Im tearing my hair out as I have run out of ideas on how to troubleshoot this problem.

While playing a game a few days ago my screen suddenly went black. So I restarted, just after booting into windows it happened again. So I tried a different monitor but the same thing would happen. For a while at seemingly random times my PC would go into some sort of hibernation mode from where it cannot be woken. It was still on, though completely unresponsive and the screen totally blank. I tried to check bios settings, booted into safe mode and tried to run the diagnostics on my Dell resource cd. However the problem would always persist so I couldent get very far. I have verified that all the connections are fine and that all the components are seated properly. I have tried several different monitors and power leads.

A day or two after that it got stranger. I can now boot into windows and everything will be fine unless I play a game. When I try to do that a seemingly random amount of time later, bang, black screen. I have run a deep virus scan using NOD 32 it cleaned a few thing out but didnt help. I have run the Dell diagnostics program it verified the CPU, Memory, Video adapter and BUS but threw up an error when checking the DVD RW. However even when I play games that require no CD/DVD the problem happens anyway.


Im running a Dimension 8400
P4 3.0Ghz
1024MB DDR2 Ram @ 400mhz
PCI-E Ati X800 XT
x1 30GB Sata HDD (shipped with pc)
x1 120GB Sata HDD (installed later)
DVD +- R/RW (installed later)
Non dell CRT monitor
Windows XP home with sp2

Please can anyone help? I have run out of ideas and cant use my system for its primary purpose, games! Any help is greatly appreciated.

It sounds like it is choking for power. Are you still using the stock power supply? If they use the 250 Watt PSUs in the 8400, that would be asking a lot of it. It would also explain why it quits when playing GPU intensive games.