Do you mean DOS or an NT command prompt? AFAIK, most BIOS updates are done in either DOS or GUI Windows. A command prompt only NT is a bit tricky, and not very useful anyway. A DOS booting USB stick ...

Before Windows 95, most PCs used to boot to DOS by default. While most of the time it led to people typing “WIN” at the C: prompt to get back to Program Manager, booting to a command line was ...