How to kill hung windows 7 update process.

I have had several experiences where windows 7 launches an update when I start my computer. In these cases there is a message saying not to shut down the computer - it will a utomatically shut after completion of update.

Problem is the the update can take over a day - and even then I am forced to force a shutdown and restart of the computer to get out of it.

My  questions are

1  Is there a way to interrupt these 'hung' updates  ? like alt plus F4 or something like that

2 I am going to stop automatic updating, but having done that, are there situations where MS can override my setting and launch an important update anyhow ? Need advice about that.

Thanks for any help.