Noticed onboard AC97 sound had a weak back channel so decided to buy a cheap
Aopen AW-850 as I'd also just bought a set of 5.1's.

Install went fine yet I did notice during driver install for sound card a
little quick flash having something to do about media player. Tested sound
etc., happy went back to life. Next evening go to play a video and it's
upside down in WMP9!!! Tested others I'd already watched and same thing.
PowerDVD also mimics same behaviour. So far only Nero's Showtime is
displaying them properly.

Anybody have any clue what might have happened. Nicest would be it's a
simple registry edit to fix?

Otherwise, at this point, it looks like maybe go back to a restore point and
see if I can't "bust out" just the sound card driver, edit the inf if need
be if it's available.