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Just a FYI....I had this exact problem in the last 30 minutes. (Windows 10) Even though the program appeared to be in the Program Files folder, with the new icon, it kept opening as PM5. The Icon on screen was also still PM5. I went to Settings and Add/Delete programs and both versions were there so deleted both and downloaded PM6 again. All good now and opened properly. (BTW, problems I had with Twitter uploads and my IPTC fields missing tabs which I spent weeks trying to resolve last year seem to have been resolved by the upgrade so happy camper here !!! )