Make sure you have the latest drivers for your video card and install the DivX and XviD codecs from the net if necessary. Also make sure that you have all acceleration features enabled in "Display Properties / Settings / Advanced / Troubleshot" and "Control Panel / Sound and audio devices / Audio / Advanced /Performance" and you're not running other programs while you're running the movie. Than run a Check-Disk (Scan-Disk) and restart your computer.