Lenovo Y50 won't open anything?

Haven't been on my Lenovo for awhile so the first time I go back on after a few weeks, I need to update. But I can't even do that now since a ton of things have popped up, so at some point I accidentally decline the update & now none of my programs will open up. I can't go into my control panel, or settings to fix things. If I click on anything else, games, Internet, literally any program, a window pops up saying "Windows can't access the specified device, path, or file. You may not have the appropriate permission to access the item." I can't even power off my computer on the desktop because there's no power options anymore?! Literally can't do anything on my laptop, highly frustrating.
How can I fix this problem? I just wanted to play games on it. I really don't do anything else on it.