Okay so here's the crack: My PC seems to completely lock up when accessing files on my network, or doing a speedtest. Just completely freeze, music stops playing; the lot. I can play games for hours, stress tests are no problem either. I've tried running Windows Memory Diagnostic on full, doing 4 passes and didn't find anything. Moved from 7 RC1 to a full RTM version which still didn't fix anything. Any ideas? Cheers.