"private" folder moved to Trash. Can not start computer.

Hello! As a product of insomnia I was cleaning up some stuff on my computer when I noticed a folder labeled "private" in my MacintoshHD folder. I moved it to trash, and when I realized maybe this wasn't such a great idea, I tried to move it back only to be prompted for my password. After typing it in numerous times and being rejected the sensation of utter doom came over me. I tried to restart. The computer will not turn on and stays on the loading screen (gear spinning under apple symbol on grey/white background) forever.


Please help!!! I am a student and am always (always!!) in need of my computer. I am also not horribly computer savy, so please be patient


MacBook pro running the newest OS (updated earlier today... Lion?)