Gigabyte 8800GTS crashes on 5 diffrent games - Help

Okay, the thing is I got a Windows Vista 32 bit Ultimate OS and a Gigabyte GeForce 8800GTS graphic card.

4xgb Corsair 800mhz cl 5 Intel Quad 9300Q on a gigabyte ep35-ds3r motherboard.
My computer is 1 month old.

The games I have are:
Neverwinter Night 2 (came with the graphic card)
BioShock
Unrea Tournamentl 3
Crysis
and Assassin's Creed.

AND THE ALL GET STUCK - Crash occur after 10-60 minutes of playing. Sometimes there's a blue screen for about 1 second before the computer reboot itself (so I can't even read what it says) and once I got this message after a reboot:

Sometimes the computer reboot itself after a while, sometimes I reboot myself and sometimes I don't have to reboot and just close the game from Task Manager.

(Those are all the clues I have for what makes my games crash)

I have downloaded and installed all the drivers for my motherboard and for the graphic card and NOTHING changed! (175.19_geforce_winvista_32bit_english_whql) <---this is the driver.

Someone suggested me to try and disable TDR (after a long research on the internet, I still don't know how to do it)
I have also been told to try and change DirectX's options so my FPS won't go below 10 (I searched this one too, but I can't find a way to do this either...)

I've been carrying this problem for weeks. Please help me.
THANK YOU!

I had this error and thought it was my video card also, and it too is a 8800 gts, if your getting the nvklkhm error with it, or something like it, its more then likely ram, i pulled both sticks, put one in at a time, and ran aqua mark, on one stick, most times it crashed, sometimes it made it, but it never ran 2 runs of aquamark concurrently. The other stick would run it everday. And memtest is great but it never detected the error my ram was running, so dont rely on it whole heartedly, pull the sticks and test one at a time, anywho after a rma, and my new 2 gig stick showed up, this error went away, and ive never had one again.

Hope your graphic card is a good brand ( Not Diamond )
Did you OC graphic card ??
Run HWMonitor_108 and keep it running to monitor your GPU temps
Either Run 3DMark 06 or play a game for few minutes the quit
See the GPU Max Temp recorded
If it is above 70 download Riva Tuner and increase GPU fan speed to 60%
Last thing comes to my mind but it is a long thing to do
Install Win XP and run these games
Could be Vista issues

ok idont overclock and i have ran 3d benchmark and the resault was 99xx.

i have a thermaltake 600w ??(dont remmember the name but its a good one).

cant i cheack both of the memory sticks at the same time if so with what program?

here are some of the replay i got on nvidia forum:
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"you should set ingame settings that FPS never drop under 10.

Or you can disable Vista TDR and then you are fine.

Apparently these drivers do not conform Vista WHQL, because then you would not have this message http://www.microsoft.com/whdc/devi [...] mspx&#034;
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i replayed to that guy:
"1)how do i reach the place where i can change the fps i went to my nvidia control panel thingy and its not there.
2)regarding to cancelation of the tdr
i typed regedit and went to:
HKLM\System\CurrentControlSet\Control\GraphicsDrivers.

but i cant find the option: TdrLevel: REG_DWORD.

so i cant turn it off.

please help me in a more precise way thanks"
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and he didnt came back to me regarding what to do can you guys?

k i ren hu monitor and my 8800gts went from 65c on desktop to 85 c in assasins creed(the game i get stuck the most).

are these temp's normal if no what should i do?