I am not a windows user per se. But do you have any utilities to check out if your ram is working ok? One of your ram chips might be malfunctioning, else always had a problem, else have a loose connection.

No I'm pretty sure my RAM's OK, I ran a medion system diagnostic and it was all green for the hardware. I'm not sure whether it helped but I uninstalled Divx (looking at the similar forums)

Thanks