Can't resize desktop display size

What's the operating system?

I'm using Windows XP SP3 Home Edition.

Okay. For the next troubleshooting steps, we need to have the installer of the video driver. Open "Device Manager" and check display adapters.

Scenario 1:

If video driver is properly installed, there will be no splat (yellow "!" or red "x") on display adapters. Click the "+" on the left side of "display adapters" then right click on the "name of the video driver" and click uninstall. Follow the prompts and if it tells you to reboot, do so and if not, just proceed below. Next, install the video driver from its location. (driver cd or hard drive folder). If it ask for a reboot, restart pc. After restart, it should be fix already.

Scenario 2:

If the video driver is not properly installed, there will be a yellow "!" on the "name of the video driver" under display adapters. Right click on the "name of the video driver" and click uninstall. Follow the prompts and if it tells you to reboot, do so and if not, just proceed below. Next, install the video driver from its location. (driver cd or hard drive folder). If it ask for a reboot, restart pc. After restart, it should be fix already.

Scenario 3

If "Display Adapters" is not seen or "Other Devices" shows a yellow "?" on video controller, the video driver is not installed on the computer. Steps to do are as follow: Install the video driver from its location. (driver cd or hard drive folder). Restart the pc to complete the installation. After restart, it should be fix already.

Thank you! It worked great for me. My problem fall on your scenario 3. For some reason the video driver got uninstalled. After reinstalling the video driver, the desktop display size is the same as it used to be. Thanks again! Good stuff and excellent explanation!