How to Change the Main Display in Windows 7
If you have more than one monitor or display connected to your PC, then this will show you how to change and make one of these selected displays your default main display in Windows 7.
You can also drag and drop the monitors to arrange them in the order you want them to display.
1. Right click an empty space on your desktop, and click on Screen resolution. (see screenshot below)That's it,
2. At the top, you will see your current main display with the Start Menu in the lower left corner, and will see "This is currently your main display" under it. (see screenshot below)
NOTE: If you do not know which monitor is which, then click on the Identity button to display the number on your display(s) to match them with.
3. At the top, click on the numbered display device (ex: monitor or projector) that you want to make your main display to have it's border highlighted. (see screenshot below)
4. Check the Make this my main display box, and click on OK to apply. (see screenshot below)