No matter what OS you are on, make sure the computer is off until you figure out what you are going to do. When/if you do turn the computer on, make sure you do not open any programs that you don't need to for the sake of recovery.
If its Windows, there are numerous recovery tools that can recover deleted files as long as you haven't done any serious writing to the harddrive since the incident. Just search on Google (
http://www.google.com/search?sourcei...=data+recovery). I think there are some free tools, or at least shareware that will do the trick.
If it's some other OS, I'm sure similar tools exist, but I don't really know of any.