A biometrics signal input device with a USB interface is connected to a computer apparatus to control BIOS booting procedures of the computer apparatus. The computer apparatus communicates with a USB controller of the input device through the USB interface according to a USB communication protocol and regards this device as a USB device. Then, the computer apparatus executes a program stored in a memory of the input device and enables a biometrics sensor to read biometrics data of a user. Then, to-be-identified biometrics data and biometrics template data pre-stored in the memory are transferred to a main memory of the computer apparatus. A CPU of the computer apparatus compares the to-be-identified biometrics data with the biometrics template data. After the comparison passes, the BIOS booting procedures are allowed to be continued until the CPU has completely loaded an operation system stored in a main storage device of the computer apparatus.