Windows 7 Ultimate crashing - ntoskrnl.exe

yes, I tried each memory individually and one crashed immediately, but the other one is working since yesterday without a problem, don't worry about that, thanks for your help! :)

Just to keep you updated, I recently got a new ram stick from the seller, and it seems to work perfectly, so now I'm sure that the problem was just the other stick, again, thanks for your help :)