Wired problem with my PC

[josephe]

Weird problem with my PC

Hello everybody!
I have a very weird issue with my pc.The computer is running smoothly and fast then suddenly freezing and I cant do anything just wait a couple minutes while it comes back again.I have tried to play Battlefield 3 and this is the same the computer is freezing or shuts down.I tried everything to sort out the problem with the best of my knowledge but it is not enough.So now I need your help because I dont know what to do next.
Things what I have already tried:
1) I have tested my memory modules with Windows Memory Diagnostic and Memtest---no errors found
2) Disconected DVD drive and external HDD
3)My CPU is overclocked from stock 2.4 Ghz to 3Ghz and the memory modules are running on 5-5-5-15 2T timings.Did checked temps the cpu is running on 46 C on 100% load the GPU is 70 C when playing Battlefield 3.Tried to restore default settings but it makes no difference.
4) Test HDD for bad sectors or errors
My config is:MSI P7N Sli Platinum - mobo
Intel Core2 Quad Q6600 2.4Ghz overclock 3Ghz
4GB Corsair Dominator DDR2 1066Mhz
MSI GeForce 8800 Ultra 768 MB DDR3 384-bit
250 GB WD HDD 7200 rpm + 500 GB external HDD
Power + PSU 750W 54A
OS:Windows 7 Ultimate 64-bit
If you have any ideas I appreciate every little help.
Thank You!

 

[2048Megabytes]

Try running the program Memtest86+ for at least 6 hours on the system and see if you get any errors. If you do not find any error codes running Memtest86+ for at least 6 hours try backing up all valued data to a separate storage device and then re-installing Windows.

I would also try cleaning off all old thermal paste and putting new thermal paste on your processor. Also run the system at normal stock speeds and get rid of the overclock.

 

[claptonman]

Have you updated the drivers for the video card? What resolution are you playing at?

 

[typhoonblue]

try to uninstall all of security tools and useless driver.

 

[josephe]

I had run memtest86 with a bootable USB- no errors found
I tried intel burn test with standard and max settings- the test was successful and the system is stable.
I have reapplied the thermal paste(have bought arctic MX-2) on CPU and GPU as well.
I have tried to put back the BIOS to default settings but is exactly the problem.
I`m playing BF3 on ultra settings on 1280x1024 resolution.