If you want to open the Command Prompt window on your Login screen or the Boot screen in Windows, here are different ways to do it.

Highlight your preferred CD or USB drive and press Enter. Alternatively, you can set your computer to always check for a bootable CD or USB drive and change the boot order.

This tutorial will explain how to open an Elevated Command Prompt in Windows 10. You can use this Command Prompt to type commands that will be executed with Administrative privileges.