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.

You can open the Command Prompt on a PC by right-clicking the Start icon, by searching for it, or by opening the Windows System folder.

The Windows Recovery Environment Command Prompt is a text-based console that allows that allows you to perform many tasks on your computer by typing in the commands that you would like to execute ...

An unpatched exploit in Windows 7, Windows Server 2008 R2 and Windows 8 Consumer Preview allows a user to launch an elevated command prompt by manipulating the sticky keys function.