What Microsoft is seeing is the proportion of their base that upgrades is not as high as it used to be. For a lot of people today, they buy their PC, they plug it in, it gives them access to the Internet and that's what they bought it for.
Microsoft has been relatively less able over time, to persuade their installed base to make the switch. People are just happy with what they have already.
Microsoft is taking steps to include its Hailstorm services into all of its products. Hotmail can be expected to be a key beneficiary of that integration.
Microsoft would no longer have guaranteed placement on users' desktops. That would mean its ability to leverage the desktop in terms of selling other services would be severely reduced, or it would have to negotiate directly to get that leverage.
The question is, to what degree can Microsoft integrate what's on the operating system with the services it offers on the Web and avoid tripping over the antitrust issue? I think Microsoft is very sensitive to this.