Ok but i have no crashdumps it seems to be related to the GPU and I sended my laptop to acer 4 Times !! they just changed the ram sticks and thats all and they said they tested the laptop and everything is fine but it's not let me explain the problem:
So I turn the system on I work with it like let say 4 hours and if you do some video related stuff (sometimes not) it crashes random (No BSOD no crashdumps) sometimes it even crashes if i just open windows live mail
I tried something called Powermizer Switch seemed to fix the problem but :| with that patch my GPÜ goes to 85 °C so

I need another fix or something I have the lasted beta drivers for my nvidia card still happens (with non beta's to)
Though I also had a problem with my Acer laptop your problem is more similar to the one I had in my ASUS laptop if I'm understanding you.
You're saying it randomly crashes but doesn't BSOD or dump anything... are you saying that the PC locks up? freezes? Or what?
If graphics drivers have no effect on this, but it never recovers itself from the crashes (freezes) and swapping out the RAM sticks didn't fix anything, I got one question I suppose.
Does it ever happen when you're not touching the computer or using a program? Has it ever frozen while idle?
My ASUS laptop has had problems with freezing randomly (I could go for 3 days up time and freeze in a browser, or freeze 30 minutes after booting with a full screen video on) but everything checked out normal and I actually tried a couple non-Windows operating systems just to make sure it was a hardware issue. I was never able to pinpoint it, but late this past summer, I replaced the 60 GB SSD in my desktop and decided to put it in my ASUS laptop just to see if it would "go stable". And it did. I'm not telling you to get an SSD btw, just concurring with Originality that it may be your hard drive if I understand you right.