Start the computer in Safe Mode – The second way to get back your original display settings is to start up in Safe Mode, which basically loads Windows in a stripped down state. Safe Mode loads up at a lower resolution and therefore allows you to log in and change the settings back.To start up in Safe Mode, you simply press and hold the F8 key when the computer starts to boot up. This is usually when you see the manufactures logo and the BIOS being loaded. Once you press F8, you’ll be presented with a set of options as shown below:
Fonte: Corrigir tela em branco após alterar as configurações de exibição do computador