No video in Media Player 7 – codecs?

Problem: can’t see any video playing MPEGS. No MPEGS show video; sound plays as normal; only the title of the video is displayed. Same problem occurs with MP6 and RealPlayer 8.

I have tried uninstalling/reinstalling MP7 and RP8; I have also followed the instructions from the MS Knowledgebase for resolving the problem, without success. I have tried uninstalling the video codecs and reinstalling them.

All ideas appreciated.

OS: W2K SP2, MS Media Player 7.

Hardware: Athlon 1GHz, 256MB RAM, 40GB HDD, Matrox G400 Max, Soundblaster Live Value.