When you change the display resolution from high to low, using Fast User Switching causes the desktop to not display, or display at an incorrect display resolution.
This behavior occurs because Windows XP doesn't save the updated display resolution when you switch between users, choosing instead to use the previous resolution from the registry.
To workaround this behavior:
1. Start / Run / desk.cpl / OK.
2. Select the Settings tab.
3. Adjust the resolution using the Screen resolution slider.
4. Press Apply and OK.