Screen freezes on boot

Hello everyone,

So that, I upgraded my PC and I have the following configuration:

P5B Motherboard
Processor Intel Core 2 Duo E8500 Box 3.16
Graphics card Sapphire ATI 4870 1024MB
Cool Master Alim (memory) 620 W

At first, no problem (for 2-3 months I would say), now the problem is that during the first 30-45 minutes after the start, the screen freezes and thus the PC crashes and even launch applications or hungry 3D games. So after the start, after few minutes it crashes almost always, it's variable but say that during the 1st half hours at least, I prefer to leave the "heat".

Something so deteriorated in the meantime (?), I see it as a problem of "hot", except that is when the PC is too hot plant, after it there is absolutely no problem, I can run any game for example.

I hear the quality of the fan of the Sapphire ATI 4870 which would not have the value of the Asus ...

I previously had a message a little odd that overclocking should not be - I said that I did not overcloqué (that is not my department) and another message that ATI Catalist must return the default settings, the screen is ATI catalyst opens and I preferred not to touch the settings before you consult.

Brief, given the symptoms, I do not know what to consider.

So before you return the PC to check-up, I tell myself that I could do some testing with your advice and perhaps solve the problem.

While waiting to hear from you, thank you in advance!

Right click on the desktop> Catalyst Control Center> (be Advenced)> ATI overdrive> clicked the lock> check the Enable Manual Fan Control;)
HWMonitor, Everest to see the temperatures, voltages ...

3DMark06 to test the whole PC.

Furmark for the graphics card.

OCCT for the processor, graphics card and another.

Hi
a problem of hardware compatibility. -> Driver (s) to verify Compatible
as precise -> Graphics Card

reinstall your graphics card -> driver

Thank you, but I do think it is a matter of drivers, everything was fine before, and now everything works well when it is "hot" ... Finally, it's just my opinion of non-expert ...

I had already updated all my drivers last night, I will restart the PC a while ago and I got you informed