Installed video codecs, still no video !

hi,

i downloaded gspot to check which codecs in need to install. The codecs used are dx50 and the mpeg-1 layer 3 codec. Gspot reports that both
the video and audio codecs are installed cause it says “2 compatible codecs installed”. But i have the sound when playing a movie, but no video. I just see a black screen. I tried a lot of things like the k-lite (mega) codec pack, the ffdshow thing, xvid mpeg-4 codecs. I can’t see the video of all movies with all video players.
i tried wmp, bsplayer, quicktime and realplayer.

Can anyone help me ? thanx