Trying to play a video in Windows Media Player on a 32bit Windows XP Pro Operating System (with Service Pack 3 installed) takes me to this web page:
http://www.microsoft.com/windows/windowsme...&codec=MSA1

Which says:

Windows Media Player Error Message Help

You've encountered error message C00D10D1 while using Windows Media Player. The following information might help you troubleshoot the issue.

Codec is missing

Windows Media Player cannot play the file (or cannot play either the audio or video portion of the file) because the MSA1 codec is not installed on your computer.

The missing codec might be available to download from the Internet. To search for the MSA1 codec, go to the WMPlugins.com Web site


And this takes me to this web site:
http://www.wmplugins.com/UnavailableItem.aspx?codec=MSA1

Which says:

The codec you are missing is not available for download from this site. You might be able to find it on another site by searching the Web for "MSA1" (this is the WaveFormat or FourCC identifier of the codec).