I came across this issue yesterday and wanted to let you know what I found and how you can go about fixing this. The computer I saw this on was running Windows Vista but I imagine it could also happen on windows 7 or XP. Anyways, I found that the laptop had a virus and this virus had hidden all the desktop, documents, and other files and folders to make it look like you had lost everything on your computer. The first thing you need to do is make sure your anti virus program is up to date and run a full scan. After that you should also go to http://malwarebytes.org/ and downloand and run a full scan of this also. Once you know for sure you have gotten rid of the virus and or malware you can now download unhide.exe from http://download.bleepingcomputer.com/grinler/unhide.exe . Download this program and run it. It may take sometime to run but once it’s done you should hopefully be able to see your files on the desktop and under the Documents folder. **NOW GO BUY A BACKUP DRIVE AND BACKUP YOUR DATA!**. You will have hopefully learned a lesson here and realize that you got lucky but next time it could be worse. So please go buy a backup drive or use a service such as Mozy and backup your data today.
I hope this helps you as it can be a really scary to turn on your computer and think you have just lost everything.