If the user doesn't exist anymore, and there is no integer value (1 or 0) in the regsitry for the encryption (to turn encyption or/off), you could be screwed.

There are some paid for programs about the net that can decrypt data, and the free ones are a bit sucky tbh.

You can try to decrypt with a either type; However you may lose some data from the files. Best option is to send them to a data recovery company like QuickRec in the UK. (I work in forensic computing so i know this shit ) Theye are v expensive tho.

You could try messing about with loads of stuff, but it will propbably end up with lost data. If it wasn't vital stuff, I'd just say re-downlaod it or buy it again.