I thought I'd mention what happened and how to possibly avoid it. I was running Windows 7x64 ultimate and was experiencing severe audio crashes - the system would hang completely and I had to reset the machine. Initially I thought i-tunes was the culprit, but when irfanview 4.25 crashed in an identical manner whilst playing an mp3 file I realised the problem was more subtle. I re-installed the OS and drivers, installed microsoft update and then removed internet explorer, media player and media centre (I mention this just in case it is a contributory factor). I re-installed itunes and irfanview and found no unexpected problems. I then added my apps one-by-one (re-booting each time). After installing Office 2007 SP2 (I installed word & excel only) I added the Microsoft Office Word, Excel & System Security updates one-by-one in chronological order (re-booting each time). The system became unstable when I installed Microsoft Office System Security update KB974234. On removing it, stability returned - however I must add that on my original unstable image, removing KB974234 did not restore stability. Has anyone encountered this problem before?