The subject error is produced by Media Player versions 6.1, 6.4, and 7.

"This error message can occur for any of the following reasons:

The media file you are attempting to play is not a supported file format for Windows Media Player, or the media file uses a codec that is not supported by Windows Media player.

You need to update to the latest version of Windows Media Player.

The Quartz.dll file is missing or damaged.

A registry key is missing or damaged.

The codec needed to play the media file is missing or damaged."

See http://support.microsoft.com/support/MediaPlayer/wmper/wmp80040218.asp.