Thanks to the good folks at Flip4Mac,
Since Microsoft's Windows Media Player for Mac is going the way of IE for Mac, this great plug-in for QuickTime allows Macs to play WMV files with QuickTime. it works REALLY well, and even Microsoft is recommending it for Mac users. It actually works better than Microsoft's own product. It is available here for free at:
Also, for a very reasonable cost from Flip4Mac: a WMV to QT converter! Bring your WMV files into iMovie for editing!