For Windows XP: Windows Media Player 9 Series
For Windows 98SE, ME, and 2000: Windows Media Player 9
For Windows 98: Windows Media Player 7.1
For Windows 95, NT: Windows Media Player 6.4
For MAC OS 10: Windows Media Player 9
For MAC OS 8.1 or better: Windows Media Player 7.1

Other Versions: Windows Media Player
 

Click here for all versions of QuickTime free player.