Hi!
My parents recently upgraded their old PC with a used Q9550 and 8GB of DDR2 (4x Corsair CM2X2048-6400C5 800MHz). The board is a Asus P5Q-E running WINDOWS 10 Pro x64, GPU is a Zotac GT440 Synergy Edition V2.

Here is the issue: the PC freezes with all the 4 sticks of RAM, but when using only 2 everything is fine. I ran several passes of memtest86+, which showed no error at all. I tried swapping the order of the RAM, mixing it with Kingston Hyper X RAM (the RAM before the upgrade). Any of this resolved the bug. I tried a different set of dual channel RAM and it was working great.

Interesting fact:
The Windows event viewer showed up an error 14 relating nvlddmkm at the same TIME the freezes happen, but the error is gone since I updated Nvidia Drivers today (error gone but problem is STILL here).

Any suggestion would be very appreciated. 

I'm currently trying the mix of Corsair-Kingston RAM with the new graphic drivers. It seems to be stable, I'll update the post if something happens. I might underclock to 667, it may improve stability?



P.-S.: I'm sincerely SORRY for my bad EnglishSOLVED 

The recommended voltage of 1.8 wasn't enough when using 4 sticks in dual channel. I raised it to 1.9 and the system is now stable.