In addressing an issue for my parents’ laptop, I stumbled upon this handy little app. It’s a small (single exe) program that allows you to peruse the list of codecs that are installed on your machine. With the DirectShow Filter manager, you can then adjust the ‘priority’ of the codec so that it is the preferred or non-preferred codec of choice for certain videos. Plus, it’s freeware.
For example, the laptop has Tivo desktop server on it, so that you can take Tivo’d programs from the Tivo to the local hard drive and watch them on the go/free up space on the Tivo. However, upon attempting to watch the video files, audio could be heard, but no video could be seen. Checking the properties of the video file, it was using the video codec that is associated with the program I use for remote control, LogMeIn, not the MPEG2 codec that it needed. I bumped the priority of the LogMeIn codec down, restarted and voila! video playback.