Why can't I shut down/preview/sign out/ MacBook Pro 2013 since upgrading?

[iMore Question]

upgrade Yosemite can't even shut down computer. Preview does not work. Can not upgrade app's from Maverick because I can't remember my original password from purchase. I wish I had read this article about jumping to upgrades.

 

[kch50428]

Re: Can't shut down/preview/ sign out/ Mac book pro 2013 since upgrades should I reinstall with disk

Holding the power button until it shuts off doesn't work?