Uninstall the K-Lite codec pack, then
Install FFDShow-alpha:
http://prdownloads.sourceforge.net/ffdshow/ffdshow-20041012.exe?download
Play the file, making sure that FFDShow is being used to decode the file. 
Call me a bit dumb but...
Trying to play an XVid - running XP with plenty of RAM. First of all I got great picture but no sound. Then I downloaded K-lite Codec pack and get the sound, but picture is very very jumpy - almost like each frame is not linked !!!
Any suggestions..??