Winhex is what I was thinking of, but you have to pay for it?
I would not be happy if software serial numbers were stored in RAM, there is no reason for them to be. The only time I would expect it to happen would be when you first installed the software? It would be a waste of resource?
I believe that by far the most vulnerable part of memory is the swap or page file.........all sorts of stuff lives in there, including passwords!