When you use multiple monitors in Windows XP, and your single video adapter connects to two monitors, clicking the icon for the secondary monitor on the Settings tab and checking the Use this device as the primary monitor box will cause the taskbar to appear on the wrong monitor when you next logon. The taskbar appears on the secondary monitor, the desktop icons appear on the primary monitor, program windows and dialog boxes open on primary monitor.
To resolve this behavior:
1. Start / Run / Desk.cpl / OK.
2. Select the Settings tab.
3. Press the icon of the monitor that you wish to use as the primary monitor.
4. Check the Use this device as the primary monitor box. This box will be dimmed if it is already the primary monitor.
5. Press the icon of the monitor that you want to use as the secondary monitor.
6. Clear the Extend my Windows desktop onto this monitor box and press Apply.
7. Check the Extend my Windows desktop onto this monitor box and press Apply.
8. Drag the monitor icons to the correct positions and press OK.