This is a board level repair, but it is something you may wish to check. Open the case and uplug the computer - you know the standard saftey speech...
Take a look beside the mouse ps/2 connector on the system board. You should see a pico fuse or a little green thing that looks like an old style resistor. Check it to see it it shows open with an ohm meter / multimeter. If it is open, the fuse is blown and no mouse will work on the port unitl it is replaced. Then the easy thing to do would be a usb mouse via mainboard ports or adapter. You can replace the fuse, but there are risks soldering on a system board. I had frends that would actually crush the component and solder the new part to the old leads still in the system board. Needless to say this is a do at your own risk. My opinion - buy the usb adapter.
One last word. I would also be real sure that the thing you are looking at is the pico fuse... not something else. See if the manual identifies it, and also check component id numbers on the fuse to part numbers on the web.
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