Carlo has a small laptop with a USB 3.0 port. But suddenly, it won't read USB 2. What gives? Leo says that USB 3.0 is supposed to be backwards compatible as long as the plug is Type A. It could be a faulty connector, or the connector pins are dirty. The connector could have also shorted out. Shine a light in and look for some cruft, or even damage on the surface of the contacts. ScooterX in the chatroom suggests that it may be a driver issue. Go into the device manager (windows key + X) and look to see if there's a red X. Or delete the drivers and then restart to reinstall. Also check to see if power management has been enabled. Windows may have turned off USB 2 to save power.