Well, played Microsoft FSX which is well know to push cpu's for 12 hours straight, played crysis for 6 hours straight and primed it for four hours and was stable through that.
Switched on the other night 3 mins into BC2 sound crash, tried again and the same thing hapened turned on board sound off in device manager and ran for an hour no issue. Turned on lastnight after making no modifications in bios or os (except turning sound back on) and played 3 hours straight with no issue.
I'm tempted to whack in a sound card but thats £70, i was hoping that some on here might have had somthing similar and have some kind of work around as the sound on these is pretty good.