thnx Brink - my old dell monitor (2007WFP) did need a new driver but issue remains. In extend mode my main desktop shows on Monitor2 (clearly assigned to the Dell) while Monitor 1 is checked as Main...

My extended 2 screens flipped my primary to #2, the select main screen box is checked but greyed out and unresponsive. Changing dual screen settings (1 only, 2 only, extend, duplicate) does not open...