Last week the opening shots were fired in the long-anticipated battle between Microsoft and Apple to gain command of the online music business. Microsoft unveiled its new beta Windows Media Player and announced the launch of a so-called built-in Digital Media Mall that offers access to online music stores such as Napster, Musicmatch, MusicNow and Wal-Mart Music Downloads. Microsoft’s MSN Music service offers 500,000 songs at 99 cents each and is compatible with more than 70 music players. As such, it directly challenges Apple Computer, whose iTunes music service dominates the online music industry with a 70% market share, though songs from iTunes Music store can be played only on Apple’s iPod music players (unless they are converted to formats compatible with other players). The stakes in this battle are high. Research firm JupiterResearch estimates that digital music sales are expected to double to 0 million in 2004 compared to 2003.…