Video Playback Issues (help)

I'm having issues with playing back .avi movies and clips. the videos are distorteted and dont properly refresh. The videos work fine on othercomputers but on this machine its distorted and sorta pixelizes. I have the latest device drivers for all my components and i have direct x 9.0c.

system:
abit nf7-s rev2
1gb mushkin
9800p 128mb

(mods if this isn't the right area please relocate it to the proper place.)

fixed my own issue. i had corrupt codecs. Nemo Codecs to the rescue! there packed with spyway but a quick scan after got rid of it all.