The user whose mouse is not working likely disabled the touchpad (been said... just reiterating)
Open Control panel (Windows Key+R, Type "Control", Enter.)
Once in control panel, Press Tab, and use the arrow keys to navigate to "Mouse" (beneath Hardware and Sound)... press enter on it, of course. The mouse properties dialog should appear. to get the "device settings" tab, press tab until a dotted line appears on one of the tabs (on my Toshiba laptop, it's the Buttons tab). Once there, use the arrow keys to move over to the "Device Settings" tab.
If our prediction is correct, then the "Synaptics Touchpad" device in the listbox will have been set to be "disabled". Press tab until the listbox is highlighted, move the selection to the touchpad (it will probably already be there), tab again to select the "Enable" button, and push enter.
This, with any luck, will re-enable the touchpad. Assuming it will work- a USB mouse would make this far easier... (less tabbing)
I'd do a combo of the "Fn + F9" keys to disable the
touch pad at will.
THAT PROBABLY MEANS SHIFT+f9
Actually- surprisingly enough, it means Fn+F9.