Boot

See also: Operating System

From Everything2:

“To load and initialize the operating system on a machine. This usage is no longer jargon (having passed into techspeak) but has given rise to some derivatives that are still jargon.”

Booting takes place from the BIOS after which a bootloader starts up the operating system.

Dual-boot

A computer is able to dual-boot when one can chose to boot one of two (or more) operating systems from the bootloader.

TakeDown.NET -> “Boot