mice can be connected to the computer using the usual PS2 port or by an USB port (USB if the mouse supports it like MS Optical mouse)
all motherboards have a PS2 port...its like the port to which the keyboard is connected and is usually in green color.
MS optical mice have both PS2 and USB ports (they come with a PS2 to USB converter)
a mouse is connected to the comp through USB or PS/2 or even serial port. Depending on whatever port you have free or wherever you have your present mouse you can install your new mouse. YOu also get USB-ps/2 converters so there is no problem.