For Windows 7:
1. Right click any blank area on your desktop.
2. Left click
Personalize->
Display Settings. A window will open that shows a monitor.
3. Navigate to
Change Display Settings. A new window will appear showing 2 monitors.
4. Click
Identify Monitors. When the monitor you are on is the main monitor, you will see "This is currently your main display" under Multiple displays. To change this, click on the other monitor and check the box that says "Make this my main display". Click
Apply.
5. If you want to change how the mouse drags from right to left/left to right, click and drag the right hand monitor left
to the left of the original left monitor and release the drag. That will change the positions of the monitors so that the mouse
motion will be the way you want them.