Graphics problems / crashing in games

Hi all

I have some very strange system problems that has been driving me nuts for the past month or so, can any one help?

At first I updated everything but my gfx card and my PSU and at times my games where crashing all over place some times 10 mins some 1hr in.
now since then i have got a new psu but have the same GFX card. which helped a small bit,

i have tried to benchmark the PC loads and it never crashed no matter how high I pump up the res or the graphics settings.

also I have to set memory times my self as i have been told that my memory needs it. and the Bios was not setting my timings right,

memory setting below
5-5-5-18
volts 2.1
DRAM freq 1066

Am I missing some settings?

after the i set the mem stuff my self i was and oddly able to run crysis for 4hrs non stop with no crashing.

Also i get the NV something or other crash message, even tho i have the right drivers installed. I had the GFx card RMA and they XFX said it was perfectly fine. and i get a blue screen with a memory dump message.



well here is my system spec

Intel Core 2 Quad Q6600 2.4GHz
Asus P5Q, P45, Socket-775
OCZ DDR2 PC8500 4096MB KIT, Reaper HPC,
XFX 8800 GTS Fatal1ty
Samsung SpinPoint S166 160GB SATA2
Samsung Sata DVDRW x 20
Corsair Powersupply 620W Black, ATX/EPS,
Samsung 20" Wide Syncmaster T200HD,
Vista Ultimate x64


thanks for any help

thanks for the info. I'll try this later when i get home , i did try the first few steps before but not the rivatuner.

i have run memtest loads and it always passes the tests so i dont think it a RAM problem. plus i don't have the cash to get more ram :<