I have a DFI nF4 series motherboard with an AMD Atholon 64 chip 2400 MHZ. Now here is the problem. I also have one Geforce 7800 GT. I kept having problems with it. During games like Rainbow Six Las Vegas, Militia (the only map that does this) on CS...... during these games my video card just frezees out of nowhere. During some games if I wait it will come back, but then it might not. So I started to measure my temp. I was geeting 60 C before game play and 98 C after. THATS CARZY. So I changed the cooling on my video card and now I am getting 50 C max after gameplay. The problem is (even though its not as much) my games still frezee.

I'm going to say the issue may indeed lye with the PS Unit in your chassis/case.

What is the make/model of this unit ?!?

Could be one or more of the 12v rails is not able to provide enough current/power to the graphics card and the rest of the system so after awhile it freezes up.

This will happen more often then not during gameplay as this is really taxing the overall system resources and power needs.

Interesting point though I have never had (unforeseen) freezes other than during gameplay or 3D CAD drawings. (Big Ones). My PS unit is an OCZ-520ADJ
After I installed my new cooling system on the GPU some games stoped freezing (ex: MIlitia). But some of them still frezee.
Is 50 C still to hot? (After gameplay)

Nope, 50C is fine, in fact on the cooler side for either GPU's or CPU's.

Now, it's possible that there was some thermal damage already done to the GPU on your graphics card that would cause this as wll.

However, you would have to have another graphics card to test this out and see.

As for the PS Unit, OCZ makes some fine products so I would think this wouldn't be the cause of the lockups, and the fact that you mention both games and 3D apps that tax the GPU heavily, this may indeed indicate that the issue is the graphics card.

YA. Thanks For Your help, your probably right. For the past 6 hours i have been trying everything. I updated my BIOS, CPU, and GPU. I tried different settings, overcloked it and brought it back....
Unfortunatlly...Nothing. My PC just frezees (even on the LOWEST settings in Medival War 2) about 1-2 min into the game.