almost everything was deleted on my cp, windows 8 ?

I just opened up my computer, and the desktop background changed to the original one from when I first bought it. Then all my files, data, and programs in the c hard drive are gone. Is there anyway to restore my computer to the way it was before, or to get back my deleted files? I have no idea what happened during the starting process this time though.
I have a windows 8 asus.

Also, all my windows 8 apps are gone, and the control panel and everything else looks like windows 7 display and not windows 8.
Thank you!

Can you use system restore to go back to a point-in-time when it was last working?