Ran into a problem installing the Arduino Leonardo on Windows 8 yesterday and I thought it would be useful to other people (including me, when my memory fails) to document the solution.
Although the Leonardo does not require FTDI drivers, it still requires the COM port drivers to be installed. Windows 8 requires that the drivers be signed. Since the Arduino drivers are not signed, they will not install. In order to install the drivers you will need to bypass Windows Digital Signature Enforcement.
If you have a greyed out Serial Port selection from the Tools menu this should solve the problem:
- Install the Arduino IDE.
- Move the mouse to the bottom right corner of the screen so that the sidebar opens up.
- Click Settings.
- Click Change PC Settings
- In the General tab, scroll to the bottom and click Advanced Startup > Restart Now.
- Now, Troubleshoot.
- Advanced Options.
- Startup Settings and Restart.
- Press #7 for Disable driver signature enforcement. (The system will boot up now.)
- Now go to Control Panel.
- Hardware & Sound and select View Devices and Printers
- Right click on the Arduino Leonardo and click Properties.
- Select the Hardware Tab and Properties.
- Click Change Settings and authorize Windows to make the changes.
- Select Update Driver and Choose File.
- Navigate to the directory where you installed the Arduino software and into the subdirectory /Drivers. Press OK.
- Plug in the Arduino.
- Open the Arduino IDE and select the correct COM Port.