HD video skipping when using DivX

HD video (.mkv) are skipping and sometimes going out of sync.
I'm using the DivX player that windows recommended for .mkv files.
If I rewind a few seconds it goes away, but it's getting annoying.

Any ideas??

NEW HP Pavilion Entertainment PC dv5-1235dx (had it less than a month)
came with vista (unfortunately)
sound card... um... IDT High definition audio CODEC??
or am I looking at the wrong thing?:confused

Help?

 

First, download and install the newest video drivers for your system. Then try a different media player and/or a codec pack. VLC Media Player is a great player that can play just about any video or audio file w/o needing external codecs. Also, if you currently have a codec pack installed, uninstall it and install the KLite Mega Pack. It has Media Player Classic built-in to take advantage of the codecs. If neither of these options work, please post your system specs (RAM, video card, etc) and we'll go from there.