My PS2 mouse won't work on my serial port with an adapter cable. My serial mouse won't work on my PS2 port with an adapter cable

PS/2 mice and serial mice are two different devices. The ID bits returned from the mouse to the mouse detection S/W routine are different to differentiate the two devices. Mice labeled PS/2 port will ONLY work on a PS2 port. A mouse labeled serial mouse will only work on a serial port. Mice labeled PS2/Serial compatible (or a derivative thereof) can be adapted to work on either serial or mouse ports with the proper adapter cables(s). If your mouse has a single designator printed on the label on the bottom of the mouse then it is a single mode mouse.

Another twist on this problem are mice that have a slide switch on the bottom that reads MS or PC. MS is for Mouse Systems (Not Microsoft) and will not work without a Mouse Systems driver. If you have this switch on your mouse, set it to PC for standard mouse drivers.