Radeon 9700 Pro trouble

[hemolack]

I recently built a new computer for myself.

P-4 2.6 Ghz (533 FSB)
Asus P4PE Motherboard
512 MB DDR 333
Antec 400W Power Supply
Radeon 9700 Pro

Everything was fine for a couple of weeks. Then my Direct3D games started locking up. Everquest, Neverwinter Nights, Unreal Tournament 2003. I tried Quake 3 Arena to test out OpenGL. It will only run if I tweak the settings in the ATI control panel.
I've read ATI's FAQ and none of it seems to apply to my problem. I sent an email to their tech support (silly me) and they told me to....read the FAQ.
Are there any BIOS settings I should be aware of in regards to this? I have purchased some Corsair DDR memory to replace the off-brand stuff I currently have, but it hasn't arrived yet. As it now stands, I have a $400 video card that has rendered my beloved gaming system utterly useless. Please...any help would be appreciated.

 

[JimmyDean]

I would say that your problem would be power, but since you have 400watts I would say thats plenty. Try seeing if your card is overheating

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