The first is to make sure you're not using USB to PS2 adapters for these mice. Some will work and some won't. If that's not an issue, uninstall the mouse and shut down the system. Unplug the USB mouse and plug in the PS2 mouse. Restart and see if Windows can find and configure the mouse.
I had been using a USB mouse for a while but now I tried to plug a mouse in the PS2 port and the computer wont' recognize it..It only sees the USB mouse..even when the usb mouse and the PS2 one is plugged in it doesn't see it. I've tried two diffent PS2 mice and neither gets recognized. this happened once before, and someone told me to do soemthing that got the mouse recognized. I remember at the time thinking it was so simple, but I can'tremember what is was.