Started yesterday with computer hanging at "Windows is Shutting Down" . Now today the "Turn Off Computer" 'buttons' don't even respond. What could be going on???

I've seen this before (not saying this is exactly what your problem is) with computers that had malware on them. You can read this article HERE, which is posted on this site. Go through the first few steps of Grinlers suggestions (although, the entire article is great advice, and I recommend reading it all!). Follow any links to download suggested programs and also to learn how to use them.

I know that it seems long, but it's really not, and is actually quite simple!

Now, after your done with the above, try restarting your computer again. Please post back and let us know what the outcome is!