grx said:
Hi again, here is what i did:

First, i removed one of the 2 modules, leaving an empty slot. I ran memtest (3 passes) and it didn't show any error.
Then i removed the left module and i put the other in the SAME SLOT. When i ran memtest, it froze on the first pass, showing near 4 errors, thus i deduced that it was defective.
Finally i put the good one on the first slot, and in the other i put my old 512mb module: Ran memtest, 5 passes, no errors.

Now i have 1,5Gb RAM and, at the moment, no BSOD has ocurred. So i just have to wait a few days to consider my problem solved.

I just can't imagine what could have incited my RAM to fail like that. I had used it for too long without any problem. Was it maybe a PSU watt problem? I really didn't know the specs of my PSU when i installed the 9400gt.

thanks a lot
grx

could be anything. after all all machiines wear out sooner or later. Could be PSU, voltage spike, heat, etc.