If you have been eagerly waiting for a chance to play with the new Project My Screen feature from Windows Phone 8.1, here is a simple 3-step method to setup your Windows Phone 8.1 with your PC so that you can enjoy this new feature and demo to people easily.
Step 1: Download and install Project My Screen App for Windows Phone.
Step 2: Connect your phone to USB and run newly installed Project My Screen App (shortcut can be found on desktop). If it runs on full-screen, do not panic, rather press F, or Alt + Enter to make it windowed.
Step 3: It will immediately ask for your permission to project Windows Phone screen through the app.
The moment you allow it, it will start to project your screen like below:
Troubleshooting: If you find the app neither asking your permission on phone to project the screen, nor displaying anything via the app, it is likely that your past phone drivers are interfering with the new ones, and you may have to press Windows + X, and choose Device Manager to bring up the list of drivers installed on the machine. Try to remove all the Nokia drivers and the screen mentioned in Step 3 might immediately appear. If it still doesn’t work, try a PC reboot. Thanks Swagata Prateek for the troubleshooting help.
Courtesy: Mohammed Aftab.
EDIT: For more comprehensive reference check this out.