My comp has been working fine. A couple days ago I bought a 21" CRT and plugged it into the VGA socket as per normal (on-board graphics card). AC is direct from the wall socket (not via the PSU). Then I bought some 2.1 speakers, power direct from the wall socket also. Previously sound came by way of two external speakers which were powered from a socket on my old 14" monitor, 3,5mm jack into the M/Board. For some reason, when my CPU is working hard the sound stops. WMP and VLC will 'play' tracks/'windows noises', you can see the timeline moving along just fine, but there is no sound being emitted. I have to re-boot and then everything is back to normal. Problem replicates every time almost. Very weird, any ideas? Thanks.