Wondershare Data Recovery is an app that enables you to recover files that were accidentally deleted - it's even possible to recover them after a reformatting.
You need to install the app on a different hard drive than the one you are going to search for your lost files. That's because the less file activity there is in the affected hard drive, the higher your chances of recovering your data. You can select and scan whole hard drives, or just partitions or flash memories.
After the scan, you'll see a list of the files that you can recover along with the status of each. The files in green can be recovered without any trouble, while files in red will make things a little more complicated for you.
There's no perfect way to recover absolutely everything, especially if a lot of time has passed since you lost your data, but this app will certainly help you recover a large amount of files that you thought had been lost forever.
The trial version allows you to recover up to 100Mb of files.