I have a windows 7 machine with vmware and 2 monitors. The first one, with vmware on fullscreen, and the second one as the main screen with windows 7 with the browser and some applications, is there any way to toggle the screens configuration with a hotkey so it switches the main screen to the left and all applications accordingly (Vmware on full screen on the right monitor, and all applications on the left)
Not exactly what you are looking for, but winsplit revolution is fairly usefull for moving windows around. ( FreeWare : http://www.winsplit-revolution.com )
You can "throw" the active window from one screen to another by depressing Windows Key + Shift key and then left or right arrow key depending upon which monitor you want the window to go to.
I know that you you are asking to change the main display designator but I don't think there is a hot key for that. You have to go into "screen resolution" and then check the box marked "Make this my main display" after selecting the appropriate display.