Yeh thats what my thoughts were, I installed the most recent WHQL nvidia driver but still no joy I'm afraid. Have tested the RAM thoroughly in MemTest+ at 800 and 1066 with both sticks in and each stick individually in both A and B slots and haven't seen any errors in those despite getting the 8000 odd errors when I tried it before. Wondering if those errors were a symptom of something else just don't have a clue what!