if you are having problems with windows media player, you can type "mplayer2" into your run command and load up the old version. I've noticed that it plays some movie files (read: poorly encoded pr0n) better than the current version of WMP.
I also highly recommend the kazaa-lite codec pack. I used to have my own codec pack that I created over years of trying to view pr0n encoded into weird formats, and the kazaa-lite codec pack is much better, plus its installer lets you choose what to install.
www.kazaalite.tk