Computer hangs when restart is selected

[John]

I can't restart my computer any longer. The computer
will due a shutdown with no problems. But, when I select
restart, the computer hangs indefinitely at the
message "Windows is shutting down...".

I think that I have tried everything. I have installed
all the latest patches and drivers. I have removed all
extraneous programs. I have tried to manually end
services and tasks. But, the restart process continues
to hang my computer.

Any ideas?