Why isn't my trackpad working after updating Windows?

Sam had three laptops upgraded to Windows 10, but one won't work with the trackpad. Leo says that a driver may be missing. Leo recommends going to the laptop manufacturer website and looking for a driver package for his laptop. If that doesn't work, he should try using the Windows 8.1 driver. It should be OK to do so. Sam should look in the device manager for any red "X", which indicates devices without a driver.