To change your display back to its original configuration, you need to reboot in Safe Mode. To boot in Safe Mode and reset the display, follow the steps below:
While your computer is booting, follow the appropriate instructions for your version of Windows:
In Windows 2000 and XP, when the Power On Self Test is complete (after the first time you hear the computer beep), press and hold the F8 key.
In Windows 98 and Me, when the Power On Self Test is complete (after the first time you hear the computer beep), press and hold the Ctrl key.
In Windows 95, press and hold the F8 key after "Starting Windows 95" appears on a black background.
Select the option to boot in Safe Mode.
Once in Safe Mode, go to the display settings by right-clicking the desktop and then clicking the Settings tab. Then you can change the display settings back to the original configuration.
To restore the correct settings, shut down and restart the computer by clicking Start and selecting Shut Down, then Restart, then OK.
THIS IS TAKEN FROM https://kb.iu.edu/data/agjg.html