I have managed to restored deleted pictures (JPEG) using several different file restoration programs, however when I go to view the files the images are unavailable to view. I have tired changing the file extension, copying to another computer or even CD but the same error message appears in 'windows picture and fax viewer' 'No preview available'.

Any ideas welcome

Some files even though recovered may have been in "bad" condition so not all critical bits that make up the file were recovered. That's why the 'No preview available' shows up. You can try another program which tries to repair the pictures. Or try a different program to recover them. I usually obtain good results with GetDataBack or TuneUp Undelete.

The problem with recovering files within Windows is that when you delete a file, other activity (browsing, deleting/installing programs, etc.) can reduce the chances of recovering that file. Newly created files can actually be written on top of the file you are trying to recover.