It hasn't. Microsoft's growth has remained relatively stable since it's growth from '95 to 2000. Apple has almost zero impact from '98 to 2005, which is where we start to see the stock perform well.
Economics FAIL. -0.5% growth over 10 year is a loss of money because you are falling behind inflation. Based on their market cap Microsoft is shrinking at a rate of 2-3% a year in real dollars while Apple is growing off the charts. You can't say that the falling Windows brand is not a direct cause of that, and Apple's contrast with Microsoft helps that. Apple's growth has more to do with the iPod than OS X, but OS X has a lot more to do with Windows falling image than anything else.