Hmmm...if you already have the newest versions of your media players with their updates...then you might just need a codec pack to correctly display your videos instead of Windows generically rendering them for you.
Although this isn't much, it is clean freeware that might finally render those videos correctly. Explore the free-codecs site as you may find better packs to download and use. I hope this finally solves the video problem.
try googlng a video player called VLC (video lan project) it plays almost everything and installs basiclly every codec into ur quicktime/windowsmedia player/realplayer folder