Computer suddenly resets (sorta)

My computer has Win 7 on it.

You know how when you make a new account on your computer, all the programs and stuff are there, but the desktop background, all the settings, bookmarks, histories, pictures, and files that aren't in My Documents are not there so that the new user can start fresh?

This is what happened to my Administrator account.
There is only this one account on my computer, and it seems like after I shut my computer down for the night last night (it didn't update or anything, just a normal shutdown) my account suddenly turned into a new account, still with the same password, same user picture, and same name. I am the only person who knows my password for my computer. Please help me. All my stuff is gone (sorta).