Strange system crashes

[Saber21]

My system is:
Gigabyte EP45-DS4, Q9300 @ 2.5 Ghz, 2x2 BG RAM GEil USA (Black Dragon), Gainward Nvidia GTX 260 (think its limited edition), 2 x 500 GB Seagate ST3500320AS

It randomly crashes in video games and I don't know why. The fact is it crashes only in certain ones. I reinstalled video drivers and windows but to no use.
I can play for example Prototype with everything at max and it works like a charm but at some points i will get a black screen (the check cable does not appear), the sound gets stuck (looping a small chunk) and no error messages or anything that would suggest where the problem lies. If i reboot my pc it does not boot it resets 2-3 times then the speaker gives a long beep followed by 2 short ones (the manual says something regarding video card or monitor) i have to power of the system in order to restart it.
I have the same issues in Crysis at very high (even if i set it to low its the same problem)
I let 3DMark Vantage run for 6 hours straight and even though i got 2-3 frames at some points it kept on going.

My bios settings are at optimized defaults and no overclock-ing was done.
What is the problem with my system?

[NimrodAUS]

Its possible that your video card is faulty or it could just be a driver problem. firstly if you are running optimized defaults then i would go into the BIOS and manually set a few things like ram voltage and maybe the basic timmings for it. I would clean ur video drivers off and install fresh the latest drivers and see. Be good if you had another video card to try out.

[Saber21]

I have already tried reinstalling windows (both Vista SP2 and XP sp2) and latest drivers and no go.
I tried a different video card and it seemed not to crash but I can't really compare the 2 (it was a nvidia 6800) If my video card is defective how can I prove that it is ? I mean the service guys will just test it a couple of hours in some sort of benchmark ... problem is it will pass :(

[NimrodAUS]

ahh well since you have tried two different OS's then the next step is to run memtest 86+ v4.00 for at least several passes. follow sucessful memtest with 4 hours of prime 95. I fear though that ur video card may be the problem here though. What PSU are you using?

[Saber21]

My PSU is Corsair HX850W. will try the mem and prime tests and report back.

L.E. 5 hours and 15 minutes in memtest resulted 6 passes and 0 error so my ram is OK.

[NimrodAUS]

Well your PSU is up to the task. And 6 passes on the RAM is plenty. If you pass a few hours on prime 95 then I'll be confident that you video card is possibly dying. If its under warrenty then get an RMA and send it back.

[Saber21]

5 hours of prime 95 and no crash Real Temp 3.00 reported max temperature on cores 65-65-59-59
Damn guess Gainward suck at video cards.

Ty for all the help Nimrod and if I may ask can i get a good configuration for my bios? no overclock?

[NimrodAUS]

I presume No crash also means no errors in prime? If this is the case then Its probably safe to say that your system is pretty stable. The problem lies with your video card or driver problem. But as you said you have tried reinstalling OS's much like I did when I was having issue with a dying card. Is it still under warranty?

I will endevour to get you are nice BIOS template up asap. I broke my collar bone on saturday so typing is inhibited and painful. lol. What speed ram is the one you got? they make that black dragon in 667, 800 & 1066. i will need to know for best possible motherboard set up. infact the exact number off it is requiered. DDR2 Black Dragon Dual Channel
PC2-6400 800Mhz C4, C5 & C6 BLACK DRAGON DUAL CHANNEL
SKU#: GB22GB6400C4DC l GB22GB6400C5DC l GB24GB6400C5DC l GB28GB6400C6DC ?????????????

http://www.geil.com.tw/products/list/id/28

[Saber21]

sorry for the long response time.
Here is my full system spec (and yes prime95 did not report any errors)
CPU: QuadCore Intel Core 2 Quad Q9300, 2500 MHz (7.5 x 333)
Motherboard: Gigabyte GA-EP45-DS4 (fios version F9)
RAM: 2x2GB GeIL CL5-5-5DDR21066 5 (1066Mhz)

And sorry to hear about your injury, hope you will have a fast recovery.