How to install ADB Driver on Windows 8 x64 [64-bit]
ADB Driver Installer (Automatically)
In Windows 8 (8.1) 64-bit you are unable to install unsigned drivers because the system enables driver signature enforcement by default.
Select Troubleshoot
Advanced Options
Select Startup Options
Restart
Press 7 or F7 to choose Disable driver signature enforcement.
Note:
Temporarily, the setting will return to its original state after restarting.
Install Android ADB Driver using an inf file (Manually)
Windows encountered a problem installing the driver software for your device.
Windows found driver software for your device but encoutered an error while attempting to install it.
The hash for the file is not present in the specified catalog file. The file is likely corrupt or the victim of tampering.