Boot in text mode ("tinycore text"), and see if there's any kind of mouse recognized:
dmesg | grep -i mouse
If it is, you should see something like
input: PS/2+USB Mouse as /devices/pci0000:00/0000:00:1a.1/usb4/4-1/4-1:1.0/input/input3
or
input: ImExPS/2 Generic Explorer Mouse as /class/input/input3