Your version of the application is old and discontinued. As years passed, the original application was replaced with an advanced version which now is called DesignCAD 3d MAX V22. You should obtain the new version for Windows 7.
If you have windows 7 pro you should be able to install Virtual XP. XP was the last program that would run the older DCAD programs. I ran DCad 7 on XP. You should still get the newer versions so you can import and export to other programs.