When you last uninstalled RB, did you use Sierra`s uninstall routine or just `Delete` the RB3D folder?
That`s what I did last year and I couldn`t reinstall from the CD just as you describe. It still appeared in Add/Remove programs from Control Panel and I couldn`t get rid of it. I couldn`t reinstall RB until I`d removed the old entries by going into the registry (shudder).
Last May someone else had this problem and we managed to sort it out on the SWWISA forum. A search for thread 1108.1 should help you. Good luck.
http://forums.delphiforums.com/swwisa/start Cloudnine
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"Rather fail with honour than succeed by fraud." Sophocles