[B Knotts]

It seems to me that Microsoft has every right to do this on updates to the core operating system, and subsystems therein. They have no obligation to provide an update service to those who do not purchase their software.

Doing it for freely provided add-on software would seem to me to probably be fine, too.

However, doing it for something like Office would seem legally questionable.

[Bush2000]

However, doing it for something like Office would seem legally questionable.

Nope. See the previous post. The EULA is the governing agreement between you and MS. When you agreed to use the software, you agreed to its terms -- and it clearly says that it won't install the software unless you're running a legit, licensed copy.