wmp aspect ratio problems with vista codec pack

hi, I've just installed vista codec pack and when I play movies on wmp 11, the movie size won't go wider than what looks like 4.3 or something like that, so if I'm playing a widescreen movie, it ends up tiny in the middle of the screen even though the player is on full screen.
I've had it working ok in the past but have had to re-install all my software onto a new hard drive. before I used wmp 11 with K-lite codec pack (I think) and it was working fine.
any ideas before I start uninstalling stuff?

 

I'll give that a go - though I've had problems with revo-uninstaller in the past: self inflicted problems, admitedly - I tried using it to uninstall windows live writer and it found several thousand leftover files which I couldn't be bothered to check through, so I just deleted them all. after that, things didn't work very well and that's why I'm now re-installing my whole system.

thanks for the links too.