On Windows 8, 8.1, Server 2012 and Server 2012 R2, unsigned drivers are blocked by default.
Follow the procedure below to allow Windows AVFS driver installation:
1. Open a Command Prompt (Run as Administrator)
2. Enter the following commands:
bcdedit.exe -set loadoptions DISABLE_INTEGRITY_CHECKS
bcdedit.exe -set TESTSIGNING ON
3. Restart your computer