It should be possible to recover the files, however it has been a long time. If the sectors of the hard drive were they were located have been overwritten many times they may be harder to retrieve....
a possible program to run is Recuva from Piriform. its simple to use and should list any files deleted on the drive ( even "securely" deleted files if you look through the settings ) i have had good results from it in the past. http://www.piriform.com/recuva
< a link with download/information on the product.