Wondershare Data Recovery is an application that lets you recover files that you've accidently deleted, you can even recover them after having been formatted.
You'll have to install the application on a hard disk that is not the one you want to recover the files from. The less amount of file movements in the affected hard disk, the greater the chance of recovery. You can select complete hard disks, as well as partitions, or flash memories.
Afterwards, you'll see a list of files that can be recovered, indicating the status they are in. Those in green can be easily recovered while those in red will be more complicated.
There is no perfect method that will allow you to recover everything, especially when a long time has passed, but with this application you'll be able to recover a great deal of files you thought were lost forever.
The trial version lets you recover up to 100Mb of files.