Nvidia Card Locking up...Part Duex

So the new thermal paste helped for a couple of days, but then it started to overheat again. So I took off the side panel and kept a box fan pointed at it. That worked for a couple of days, but the inevitable happened. It once again started to over heat after 30 or 60 minutes of playtime. So I just decided to get a new video card.

I couldn't find another 5950 FX Ultra to just replace it, so I ordered a Geforce 6600 GT. After I installed it and started up WOW, the picture was streaking and popping like a really old movie played on an old projector. I've installed both the drivers on the installation cd and updated ones from Nvidia's site, as well as the old drivers my 5950 ran on, but the streaking is still happening.

So I'm left to thinking that this might be because my power supply is too small. The cards' specs call for a 300 W and mine is only 280 W.

Could this be what is causing the streaking? Do I need to upgrade to a larger power supply?

My other parts if this helps:
Mobo - Soyo KT600-8237
CPU - AMD Athlon 2 ghz
1 gig of RAM

First of all what Brand is the PSU...If it's a Brand Name it should be fine.
Your New Card could also be faulty...Chit Happens.
Back when the ATI X800 series came out I went throught 3 to get a good one....and when I had a 7900GT that died after 1 1/2 years it took 4 RMA's to get a good working unit.
I would take back the 6600...sounds faulty to me
Another thing what is your buget for a new Videocard???
There's better cards than the 6600 nowdays for about the same price.

Well, I really am trying to get a low cost card for this computer because I plan on buying a new system in the future just not the immediate future, so I don't want spend more than $50-60 on a video card. Plus my mobo is AGP, and I figured my cpu would just bottleneck any performance gains from a higher level card.

Anyways, I bought a 450w power supply because that is one thing that I can put into my new system whenever I can get to build it. It helped, but it didn't seem to help much though. So it probably is a defective card.

But real quick, I did notice some other things that might help. If I lowered the resolution on my monitor and increased the refresh rate, it helped somewhat with the tearing. However, it is still noticable and whenever I am inside a building or a cave sections on the walls flicker like flashes. I also thought that the problem might be that my monitor just wasn't connected snuggly enough. So I looked, and the VGA connector was missing one of its pins.

I'm not sure if that could cause the glitches, but I thought I'd mention it. I'm not sure if the missing pin is a new development or not. The monitor is 10 years old and I got it used from one of my old roommates about 5 years ago.

Well I would exchange the 6600 if you can.
Just looking on Ebay....You can get a 9800Pro for $37 ...which in my opinion is a much better card...Ya the 6600 will bench better ,but in real world gaming I found the 9800 Pro with Omega 4.10 Beta drivers to blow away the 6600.
I bought a 6600 years ago and thought why pay $235 for something that gave me less FPS in any of the games I played (Spearhead/COD/COD 2/Battlefield Series) JMO