Alienware M17x R3 - Heavy Lags

Hi guys it is me again !


So after I succeed to resucitate my alienware for the second time (Check the thread here), I'm having a very annoying issue again. I'll try to be as complete as possible.

So basically, when I start my computer, it starts lagging horribly, to the point that the mouse is responding only every seconds as well as the screen. The fans are going crazy too, they go from quiet to uber noisy to quiet to middle noisy etc... like if I was launching a heavy software or something. The lags can start from the boot (windows logo very slow to appear when starting the computer), or it can start lagging after 30 minutes of usage or even 2hours, and sometimes it doesn't lag at all. It is very random.
As an example, when it starts lagging from the windows icon, I restart my computer and it works fine. Sometimes I need to restart it 3 or 4 times in a row to have a normal behavior of my computer.

Here are my specs:
i-7 2760QM @ 2.40 Ghz
8GB DD3
RADEON 6900 HD 2GO
WD 750GB 7200 RPM
A08 Bios

So here are a few precision for what I noticed and tried...
-I ran some Alien Autopsy test : GPU, Hard Drive, CPU etc... passed all tests.
However I remember that 2 month ago my Hard Drive test had a time out for the test called "SMART short self test", but then the test passed.
-I tried to upgrade my AMD drivers but it won't work, back in january I had to make a system recovery after trying to update the drivers and I had a BSOD. So few days ago I downloaded the autodetect driver from the AMD website, but it says it won't install because of non -compatibility. Very Frustrating, I can't have up to date drivers.
-I am currently running a defragmentation that takes hell a lot of time.
-Concerning my GPU again, When I ran the tests, my GPU went all the way to 107C. It is almost the maximum it can handle.
After this, I played a game in High Perfomance settings, but after lagging and lagging, my computer just shutted down due to overheat I think.
-I'm always running on the balanced setting, and with this setting I never have any temp issues (GPU and CPU between 60C and 80C with very demanding games).
-I checked for Malware and possible viruses with Rogue Killer and Malware bytes.

One other thing. When I bought my computer, It was brand new, nothing Installed, and during the first two weeks of utilisation, I had to start my computer 2 times to enjoy it normally because I had the same problem (a little bit less laggy) when I first start it.

So here it is, I don't know what can be the faulty part: HDD / GPU / RAM / Battery ??

Any advices would be greatly appreciated !!!

Thanks a lot in advance !