ANSWER (more for original poster)
I read a whole lot of not answers so here is a fix that worked for me and yes I do understand your issue. At first I had a no success in fixing this ...i tried disabling the other monitor and then re enabling it ...i tried switching the dvi ports on the
back of pc ..i tried the windows setting and catalyst control setting (amd/ati cards) and nothing would actually change my 1440p monitor to monitor 1 instead of 2.
Easy fix that worked....unplug the number 2 monitor with computer on in windows and you will see the number 2 change to a number one...then plug back in the other monitor and it changes to monitor 2. Hope that works for you as well. Seems silly it was
that easy to fix since i tried so many other things that did not work...i hit identify and now my #2 monitor is #1 and both work fine.
Reason i needed this was that a game in steam that did not support 1440p normally I wanted to force -fullscreen through console and it did not work if my 1440p monitor was #2 even though it was primary