Video file based on the Microsoft Advanced Systems Format (ASF) container format and compressed with Windows Media compression; basically an .ASF file that is encoded using the Windows Media Video (WMV) codec; Windows Media audio files are saved with a .WMA extension.
NOTE: Microsoft Windows Media Player 9 was the last version of the Windows Media Player developed for Mac OS X; however, Mac users can use Flip4Mac WMV (also known as Microsoft Windows Media Components for QuickTime) to play WMV files.
Program(s) that open wmv files
Mac: Microsoft Windows Media Player; Apple QuickTime Player with Flip4Mac WMV Components; Web browser with theFlip4Mac WMV plugin Windows: Microsoft Windows Media Player; CyberLink PowerDVD; CyberLink PowerDirector; Roxio Creator; Web browser with the Windows Media Player plugin
Information from FileInfo.com - The File Extensions Resource.
http://www.fileinfo.com/extension/wmv
