The big incentive, IMO, is coming down the road. Microsoft is working toward making Windows a subscription service. The major ground work for that was started in ernest with XP and it's product activation. The next version of Windows they release could, if they go to the subscription business model, possibly have the ability to shut you out of your own computer if you don't buy a new license from them when your current one expires. Granted, there are hacks around XP's activation scheme, but Joe 6 pack probably won't go that far. MS has been pushing their corporate customers to the subscription model. There are still a lot of Office 97 out there and little reason to upgrade to Office XP since the improvements are not all that great. If people don't upgrade, it cuts into the revenue base of the company. But that's just my opinion, so take it for what it's worth.
That just might do it.
Another one I was thinking of is 'Trusted Computing'.
I stopped with Windows Media Player 8 because 9 incorporated some of this check MP3 for ? whatever they check for.
I don't play MP3 at all but this did seem to be a step too far.