A circuit for protecting a motherboard if a component is not connected properly to its power source, a startup circuit (50) connected to a switch, and a monitoring circuit (70) monitoring the status of the component. The startup circuit provides a control signal to a power supply (10) via the switch for controlling the power supply providing power to the motherboard. The monitoring circuit outputs a monitoring signal to the switch to control the switch to be on or off, so as to control the transfer of the control signal.