Thanks Richard,
Have downloaded drivers and all is running well, however the problem is centred on one particular mpeg that comes from my son's new digital video camera, and opening that still produces 'error loading codecs' in the bottom of media player before the BSOD arrives.
We have found that older mpeg's from other sources seem to play without problem, and are waiting to get hold of other files taken with this camera to find out if it's the camera or the computer that's really at fault.
The errant file plays in Real Player without problem but 'She who must be obeyed' insists on using Win Media player for most media activities including storing and playing music. Hence we are trying to get a fix for this problem.
Thanks again for your help.