By default, QuickTime does not play the Windows Media files viz .wmv and .wma. If you want to play these file formats in QuickTime, download and install Windows Media Components for QuickTime.
Play Windows Media files in QuickTime
With Windows Media for QuickTime by Flip4Mac, you can play Windows Media files (.wma and .wmv) directly in QuickTime Player and view Windows Media content on the Internet using a Web browser.
Windows Media Components for QuickTime has been highly optimized for Power Mac G4 and G5 and Intel computers and supports playback of high-definition Windows Media video files.
Check out Windows Media Components for QuickTime for details and download.