If you haven’t registered it or if you are running a pirated version you could have that problem.
No, in that case, you will get reduced functionality--your screen background will be black, there will be a "this is unregistered" note on the bottom, and info on how to contact MSFT to buy a key for the system. Eventually it will stop operating, but it is in MSFT's interest to give a user with a pirated version a chance to pay up.
By the way, the update which invalidates many "activation hacks" is KB971033.
Legitamate factory install and registered.
I did install Logitec Harmony software yesterday to change some components on the remote. I’ve used the same software on Vist and XP without problems.
The last restore point on the computer is the Windows critical update.
I was tempted to bring my computer to work with me but I can’t log onto the network with that computer.