The reqular Notes client package has an option to install for "Just this user" or "For all users of the workstation." The Admin/Design client only supports "Just this user". When you un-installed the old client it may have failed to completely clean up the Lotus software key in the Windows registry. Thus, when you tried to install the new Admin/Design client, it still sees a key that indicates this would be an "upgrade" of the code trying to install "single-user" code over the top of "multi-user" code. Un-install the Notes code using Add/Remove programs. Delete any previous code directory, (defaults to C:Program FilesIBMLotusNotes"). Then completely delete the HKEY_Local_MachineSoftwareLotus key and try the install again. Make sure that you have a good backup of your previous Notes Data folder if you need to keep anything in there.

The reqular Notes client package has an option to install for "Just this user" or "For all users of the workstation." The Admin/Design client only supports "Just this user". When you un-installed the old client it may have failed to completely clean up the Lotus software key in the Windows registry. Thus, when you tried to install the new Admin/Design client, it still sees a key that indicates this would be an "upgrade" of the code trying to install "single-user" code over the top of "multi-user" code. Un-install the Notes code using Add/Remove programs. Delete any previous code directory, (defaults to C:Program FilesIBMLotusNotes"). Then completely delete the HKEY_Local_MachineSoftwareLotus key and try the install again. Make sure that you have a good backup of your previous Notes Data folder if you need to keep anything in there.