As others have said, MS will not be releasing a product on Tuesday. Instead, they'll introduce a concept that will take months or years to get into consumers hands.
On another point, I don't know why posters here are bashing MS's handheld devices and media capabilities. Right now, the Pocket PC's (which run an MS OS) are by far the best handheld devices out there. They do pretty much everything that a full size computer can do. Palm used to dominate the handheld market, but Palm has been playing catch up ever since MS released the PocketPC operating system.
Also, MS's Media Center version of Windows is pretty awesome, and it will be even better in Vista. Maybe Apple has something good up their sleeve, but Media Center blows Front Row out of the water.
I like my Apple products, but bashing MS on handheld and media software is silly. These are two areas where MS has clearly innovated and taken the lead.