Unless the disk hasn't been reduced to dust then there is usually something you can do although the solutions get increasingly expensive the harder it is to get at the data.
Best would be if you had defragmented your harddriver regulary. Everything else will make it terribly hard to puzzle the pieces together.
Your first (i.e. immediate) thing you should do is run a file recovery program. Most of them will cost you but there is a free one:
And then, you might always give Tyberius Prime a call, he's a guru when it comes to dig through your harddisk with a diskeditor, scrambling out single files and things. But then, the plane ticket for him alone might cost more than your data is worth to you :-)