If you've recently updated to Windows Phone 8.1 and aren't able to project to a PC with the Project My Screen app and a USB cable, try uninstalling and reinstalling your phone drivers on your Windows PC.

1. Connect your phone to your Windows PC using a USB cable.

On your PC, go to Start and open Device Manager.

Click Universal serial bus devices, right-click your Windows Phone, and then click Uninstall. Be sure to uninstall every Windows Phone devices that appear in this list. (You may need to restart your PC.)

Disconnect your phone from your PC, and then reconnect it. Phone will automatically reinstall the correct drivers.