System Crash During Game Play

Hi Guys,
Having problems with different games crashing, first the screen freezes then goes blank and if I don't shut down strait away the system begins a memory dump. (Blue screen)

The games are Farcry, FEAR and the worst is CRYSIS, which is what I'm having.

After about 20 minutes of gameplay (CRYSIS) the screen freezes, occasionally the screen fills with bright triangles with movement. The sound still plays and I have to hold in the on/off button to shut down.

I'll try to give you some specs of my rig:
Graphic card - Nvida 8800 GTX OC
mob - ASUS P5KR Intel P35 Chipset Socket 775
CPU - Intel Core 2 Quad Core CPU Q6600 2.4Ghz
RAM - 4G of DDR2 667
OS - Microsoft Windows Vista Home Premium 64 bit

Things I have tried to date are:
Download new nvida driver
reinstall the games
reinstall of directx 10
added another case fan, that makes 3 x 12cm case fans.

Finally this might be a clue, means nothing to me; an automated problem report poped up with the following;

Description
A problem with your video hardware caused Windows to stop working correctly.

Problem signature
Problem Event Name: LiveKernelEvent
OS Version: 6.0.6000.2.0.0.768.3
Locale ID: 3081

Files that help describe the problem
WD-20071221-1122.dmp
sysdata.xml
Version.txt

View a temporary copy of these files
Warning: If a virus or other security threat caused the problem, opening a copy of the files could harm your computer.

Extra information about the problem
BCCode: 117
BCP1: FFFFFA8004E914E0
BCP2: FFFFF980046E35B0
BCP3: 0000000000000000
BCP4: 0000000000000000
OS Version: 6_0_6000
Service Pack: 0_0
Product: 768_1

I do regular virus checks and I use Clean and Wipe in an attempt to keep the system tidy.

I thought I spent enough money on this rig to be able to play any game, no matter how demanding, now this and I can't even tell if it's hardware or software related.

I'd be very grateful if someone could give the answers.