A computer system includes at least a first and a second operating device and a control module. The control module sends at least one signal to a central processing unit for managing and controlling the first and the second operating device, and copying the contents of any one of the two operating devices to the other operating device, so that both of the first and second operating devices include an operating system, and the computer system can select any one of the first and second operating devices for booting the operating system and power off or power on the other non-selected operating device.