If you are running Windows 10, you can use the Windows Update to find your current driver. Otherwise if it is a generic touchpad without any manufacturer branding on it, then go into Device Manager and locate Human Interface Devices. Right-click on this entry and select install driver software from disk. You will be given suggestions of what type of drivers to search for based off your devices model number. If nothing comes up there, try searching through Dell or HP instead as they have more in-depth lists that may work better than Microsofts default list