Correct diagnostics for apparent gpu problem

[Wazawaza]

Hello everyone,
I'm here to ask for some advice. I already created a topic, but it started to get confusing, so I'm starting it again from scratch.
Three weeks ago, my custom built pc started freezing and crashing 5 to 6 times in 2 days. Once, the fans sounded like they were overspinning, which was fixed with a restart or a reset.
The next 2 weeks, no problem was noticeable.
Then last week, it started crashing again, so I decided to take the gpu out, clean the fans, change the paste and check if everything was well connected.
For 2 days it worked without trouble. As it is today, my pc crashes in specific moments (playing bad company 2) and I tried bluescreenview to see if I could determine where the problem was.
Bluescreenview reports that the cause for the crash is ntoskrnl.exe.
I have 2 reports, but I can't figure out how to attach docs in my thread :S
I stress tested the gpu using OCCT for 1h30 and it went normal (hottest point at 63ºC).
Used memtest to check ram, which reported no errors.
Also checked the ssd with HDtune and Kingston ssd toolbox (which automatically reverted to a previous Microsoft visuals driver), and they said my ssd is working fine.
I also tried to repair from the win7 disk, but it shows my "local disk C:" as "local disk E:" (I have a hdd called E: and it contains a backup image of my OS, that confusion made me decide not to repair, not knowing if it would repair the image, thus creatig an OS conflict)

Here is my rig:
CPU: Q9550 quad core (fsb of 1333mhz)
motherboard: asrock g41c-gs
GPU: AMD HD6950 Sapphire
SSD: Kingston v300 240gb
Ram: 2x4gb Kingston hyperx (bus at 666mhz, I chose 1.65V)

Btw, my OS is cloned.
I hope this is not to confusing, but it's annoying to have crashes and see that everything is working well when I test the components, if you have any idea of what the problem might be (gpu possible failure or software error), I would be very thankfull.

 

[coozie7]

Sounds like that file is damaged, or one of the HDDs is failing.
If you've got the drives in a mirrored array both are likely to be corrupted.
Have a read here: http://www.ehow.com/how_5085175_replace-ntoskrnlexe.html

 

[Wazawaza]

Thank you for your reply.
I will give your solution a try. Would you know if this procedure works using the win7 install cd, or must I create a recovery cd?
I have 2 drives, 1 ssd for the OS and a normal one for files (the image of the OS is merely a backup with some compression, could this cause a conflict?)
I remembered something after posting and it may be related: I used an external hdd for backup before cloning my os (using macrium reflect).
For some weeks, the external drive worked fine with my pc, and suddenly it stopped being recognized. If I go and manage my disks, the external drive appears, but I can't access it (it doesn't appear in My Computer).
I tried Battlefield 3 for 45 minutes and it didn't crash.