Carrara has all the goodies of RDS. The interface is different and it crashes less often. I really don't use it (or any of my apps), so I really can't tell you all the details. From what I see posted in this forum, it is a good program. You should contact Eovia about upgrading from your version 4. I doubt if they got the registration database from Meta anyway. Eovia isn't selling Carrara yet, but you can still find it on line. Probably not as an upgrade, though. FYI, for me to go from RDS 5 to Carrara was $100. Meta sold the 5.5 upgrade for $100 with a free "next upgrade", which was only a few months behind the release of RDS 5.5. I think Big Serge is still selling his copy of Carrara for a good price. He has a thread in here somewhere.