I was having the same problem, I did windows update and then shut down the computer (with explorer still as the shell.) Some updates need to install while windows is shutting down. If you have the little Windows Firewall shield next to your shut down button, then that is probably the problem. (p.s., the svchost that was taking up that much cpu was running something to do with winupdate. Thanks for the tip about ProcessExplorer, DeV)