Question Windows insists on wrong Display as 1

[gr0bda]

I have a Dell monitor and and HDTV (720) connected to my Windows 10 computer.
Dell is horizontal - DVI
HDTV is vertical - HDMI
When I turn on the computer and monitor is ON, Windows sees it as Display 1. Unfortunately when I turn on the TV, Windows assigns #1 to TV!!!! Rather than monitor, which is really infuriating . Even though my monitor is set as the "Main Display" When I try to change to clone displays Windows takes orders from the HDTV and tries to switch view from horizontal to vertical instead of forcing the TV to display horizontally on vertical screen.
I know it might seem very odd, but I need this for my MAME dual screen setup. It used to work correctly on Windows 7 and even on Windows 10 , but at some point something got messed up.
On top of that MAME won't load correctly. All versions hang when launched. Also because of the wrong order MAME was showing settings screen on wrong monitor when launched. All because of the wrong order.
What can I do? All I find is how to change the monitor I want to be the "Main Display" while I need the main display to be #1 not #2 and that I cannot change!

 

[Barty1884]

IIRC, different display 'outs' (DP, DVI, HDMI etc) will take priority, but I haven't been able to determine any specific reason.

MAME doesn't prioritize the "main" monitor?

 

[gr0bda]

As of now MAME (every version) hangs. Before I had at least one that would work. Now even the one one won't.
Forgot to mention that HDTV is mounted vertically, but I want it to display horizontally on Vertical panel in cloned mode. Mame can display both screen that way. On the Horizontal I can have game displayed horizontally and then on the vertical it will clone the same display but horizontally. So clearly it can be done and handled, just POS Windows refuses to do it right.
EDIT: And just to clarify MAME works fine when I turn off TV

EDIT 2:

MAME doesn't prioritize the "main" monitor?

I don't think it ever did since I have installed Win10. It always moves the nag and settings screen to the VErtical one instead of keeping it on the horizontal one (which is marked as Main)

EDIT 3: why is this forum "retarded" When I click on quote instead of adding quote to the body of the message it displays message something like: "quote added to multisomething" Added where? Why do I have to start doing another search just to figure out how to quote on Tom's Hardware forum? Then when I don't use it for prolonged amount of time I'll have to take a refresher course on how to quote. Sheesh! Anyone heard of simplicity and convenience over there?