When Windows resumed from hibernation I got a message
Preparing to configure Windows.
Do not turn off your computer.
(Note that resuming from hibernation is supposed to restore the machine exactly as it was, it's not a time to install updates.) After two minutes this became
Failure configuring Windows updates.
Reverting changes.
Do not turn off your computer.
This remained on the screen for a full hour, so I decided to turn off the computer after all.
Rebooting results in the same messages.
I tried to run repair from my installation DVD, but "startup repair could not detect a problem".
Booting in safe mode is no avail either.
How can I get Windows to startup properly? I don't seem to have restore points.