Windows Media Player is the multimedia software developed by Microsoft to provide users with the ability to view multimedia content, both from the Internet and from their hard drive. If youve bought into the Microsoft-oriented music world in any way, however--perhaps with a Media Center PC, Portable Media Center device, or by using a WMA-compatible online music service--you simply must upgrade to WMP 10. This release offers major improvements for discovering and buying, and subscribing to content online, sports an improved UI, and integrates nicely with a coming generation of portable devices. And if up-and-coming music subscription services, like that now offered by Napster, take off, the release of WMP 10 will be heralded as the watershed moment of what is clearly still a nascent market. That said, users interested solely in music playback will likely find little reason to abandon iTunes. And iPod users will simply ignore WMP 10 as they have previous variants. Windows Media Player 10 is free and requires Windows XP (any edition), but not any other Windows variants. That decision will be controversial, but I think its the right one: With over 300 million users, XP is clearly the preferred Windows client for consumers and music enthusiasts: Had Microsoft shipped a WMP 10 variant for older Windows variants, that product would have lacked key capabilities and held up the release of the XP variant.