You can always download the latest version of RD-D from howsoft.com at the following link: http://www.howsoft.com/downloads/. I suggest you keep your copy up to date as, apart from improvements, the latest version may need to include corrections at some point. If you have already acquired a licence and Unlocking Code, the simple replacement of the program will not disable it in any way. Your Unlocking Code is kept in the main program folder in the file unlock.txt. But even if this file gets removed, all you have to do is re-enter your Unlocking Code via the RD-D Help/About menu.
Unlocking code - and how to enter it