This is a workaround for the "Missing Digital Signature" error for failed Arduino Drivers installations. This process requires that you restart your system and complete the steps while not having access to the internet so please print out these steps before starting the process or view them on a PC other than the one on which you wish to install the Arduino Drivers. If you are using Windows 8 you must disable your Driver Signature Enforcement in order to download the Arduino drivers.
Steps to disabling Driver Signature Enforcement:
1. Windows Key + R
2. Enter shutdown.exe /r /o /f /t 00
3. Click the "OK" button
4. System will restart to a "Choose an option" screen
5. Select "Troubleshoot" from "Choose an option" screen
6. Select "Advanced options" from "Troubleshoot" screen
7. Select "Windows Startup Settings" from "Advanced options" screen
8. Click "Restart" button
9. System will restart to "Advanced Boot Options" screen
10. Select "Disable Driver Signature Enforcement"
11. Once the system starts, install the Arduino drivers as you would on Windows 7