how big are the files you lost, if there small you can getsome free software to helpyou out. However if the file are big you will probably have to pay for it to be recovered.
The key about deleted files is that they don't acually get deleted at all, instead the space they take up is allowed to be overwritten whenever the hard drive next wants to do so.
So, like Bootup said, if it's a large file the chances of that happening are greater than if it's a really small file. Good luck.