Games Freezing Problems

Hi there, i was hoping someone here might be able to help me with a problem.

I have just bought a new machine

Intel Core Duo 2.66GHz

2MB Ram GeIL 2GB (2x1GB) PC2-6400C4 800MHz Black Dragon DDR2 Dual Channel Kit (GB22GB6400C4DC)

ATI Radeon X1950 Pro

Gigabyte P35C-DS3R

Corsair HX 520W ATX2.2 Modular SLI Compliant PSU (CMPSU-520HXUK)

Windows Vista Home Premium 32 bit.

To go with my machine a got myself a few new games to, this is where the problem lies.

Pro Evolution Soccer 2008 - Runs like a dream

Flight Simulator X - Appears to run fine

Bioshock - Always crashes at second load screen (although i do believe this is due to game bugs rather than my machine)

FarCry - Always crashes after about 5 min of uninterupted gameplay (always at different points)

Worlds In Conflict - Can play all the tutorials fine but will always crash about 5 min into game play (always at different points)

Half Life 2 - Crashes during video after selecting new game.

All of these crashes are my screen freezing and i can get no response from computer. Only option is to hit the reset button

Basicly does anyone know why all these games keep crashing on me. I got this pc so i could play games of this level without any problems.

I have posted this eleshwere and you can see what has been tried so far below.

http://www.techsupportforum.com/gami...-problems.html

I have also tried running memtest and windiag on individual sticks of memory but they will also freeze on test 4.

All help is much appreciated,

Cheers
Jibber4568