How were the files lost?
How did you get them back?
What message do you get when you try to play a file?
If you download a program like Explorer View for Windows Explorer from
File Viewer: Powerpoint viewer, plus Visio, DWG, Excel, AutoCad, PDF and more., does it play the file? if not, what can you seen inside the file - does it contain data or is it all 0's?