Multiples Bsod and Freezes

First excuse me for my poor english, I'm french,
Now let's say that I've got this computer since Xmas (2010), that it runs under windows seven x64 and that it's got 8go ram, 1go video (ati radeon hd 5800), a 3 Ghz processor ( amd phenom II x6) and a 600 go Hard disk (sata 3).
I have installed steam, no problem, some games like starcraft 2, fable , empire earth 2, and then games from steam, : half life one, opposing force, blue shift, counter strike source, team fortres 1 and 2, half life 2 + episodes 1 & 2, and portal.
My drivers are updated.
BUT, i've had many Bsods on the 2nd of january, then it stopped, i had the reports but i had to reload the system from before i had them so i don't have them anymore, i had to do this because bsods started again.
I recall the dumps i read with windbg: moduls implied were win32k.sys, atikmdag.sys , and hardware.
Recently i could read on the blue screen : IRQL_NOT_LESS_OR_EQUAL
A "Bsod row", as it is what happens, usually starts with a total freeze of my comp while surfing or gaming.
Then i reboot and like five minutes later, first bsod, then it's as I said a row, while starting or not.
Bsods also happens at some specifical clics, like when i click on the "malware tracking tool" update from windows.

Whats going wrong on my pc, i checked my ram, it looks allright, but...

Whats going wrong on my pc, i checked my ram, it looks allright, but...
- Give link to a web page with your RAM specs outlined, and attach the CPU-Z screenshots. This way we can tell for sure if the RAM is set right.

- Another possible cause can be the power supply.

- Or a driver bugging out.

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