From A-FF Labs:
When you delete a file, its content physically remains intact on the media, but the occupied space becomes marked as free. Next file saved to the disk may overwrite the contents of the deleted file.
It is very important to make sure that no application writes to the drive or partition where deleted file is located since every new file (even a small one) may overwrite the deleted file.
NTFS Undelete is free software that allows you to recover deleted files. It recovers files directly from hard drive, and it will work even if you empty Recycle Bin.