Instability Issues

Hi everyone,

I have my PC's I5 overclocked to 4GHz (200MHz x 20) on air cooling (prolimatech armageddon, stable at 60 degrees) with my memory at 1600MHz (at the recommended voltage from supplier). The vast majority of the time, the PC works fine, however I occasionally get a crash/restart of the computer. When Windows boots up it always comes up and says 'Windows has recovered from an unexpected shutdown'.

I'm going to begin stability testing with Prime 95 and then memtest to see what's going on. I suspect this instability may be due to the heavy over clock, as i've bumped many of the voltages a little, like the IMC, PLL as well as the core ones like vcore.

There are really no set conditions in which the computer crashes like this, however i find it to happen the most when i'm AFK, and thus there is no mouse/keyboard input. I've been through many a long gaming session where it's been fine all the way through. But like i said, i can leave the computer for maybe an hour or so, and i'll come back to the log in screen. Once or twice it's done it when i'm actually there, mostly when i'm not doing anything heavy, maybe some light music playing and on the internet. So i get the feeling it's to do with idling etc. But i can't say for sure.

But just as some early guestimation, what do you think it could be here?

See below for specs:

Intel I5 Nehalem @ 4GHz 1.4v (IMC, PLL voltages bumped slightly but can't remember exactly what)
8GB Corsair Vengeance 1600MHz @ 1600MHz (200MHz x 8), recommended voltage
Asus Maximus III
Corsair HX 850 PSU
XFX 5970 @ stock
Samsung Spinpoint F3
Windows 7 Home Premium 64-Bit

Really? Have I got the Toms community stumped?

Thanks guys. I ran blend tests and memtest and nothing came back negative. The blue screen that happens returns a code i don't recognise, i'll try and replicate the crash so as to take it down, but it's nothing to do with any of the errors that usually indicate memory failure. However, in Windows error reporting, there are reports of a critical ATI driver failure just before each of the crashes happen, so i'm thinking maybe is the graphics card. And yes the drivers are fully up to date. The plot thickens...

Possibly, i keep the registry clean using C Cleaner. But i'll give it a try. It's been fairly good the past couple of days so i never know what to think of it .

Thanks , as you can see in my sig, it's not like my parts aren't up to it lol. Stable at max 65 celsius depending on conditions.

And no, I use 2 x 4GB sticks @ 1600MHz. (Again, see my sig).

And yeah it could possibly be the sheer scale of my overclock, but like I said before, every crash was preceded with an AMD driver failure (according to Windows Resolution Centre after the crash). It also has always happened randomly on the desktop doing general things like internet browsing, Spotify etc. It has NEVER happened in game.