Need Help: Mouse Driver for Windows XP PS/2 mouse

My son's computer has somehow lost the ps/2 mouse function. The mouse
arrow appears on the screen at bootup, but it cannot be moved. Mouse
OK, tried several mice, same problem.

When looking in the CONTROL PANEL, MOUSE PROPERTIES, HARDWARE,
there is nothing in the DEVICES NAME white box, in other words
it appears the mouse driver is missing or uninstalled.

I suspect he got some kind of malware, but not sure.

Can anyone steer me right on how to re-install the mouse
drivers WITHOUT A MOUSE on the system? Or will he have
to do a WINDOWS REPAIR or complete re-install?

Any help appreciated.

Jim