I'm running 64bit Vista Business (I know, I know) and I couldn't get RGP2K to install at all. When I run the installer I get this message: "This operating system is not supported".
If any of you have this problem, there's a simple solution: Right click the installer executable and select properties, then navigate to the Compatibility tab and select the checkbox marked "Run this program in compatibility mode for: ..." in the dropdown menu, select Windows XP (or an earlier version). Run the program and it should be fine.
This was going to be a question thread until I remembered compatibility mode. Hope this helps someone.