Hopefully i am able to find one solution for this issue.
Download ‘Adb Driver Installer‘ from here http://adbdriver.com/downloads/
after this connect your Moto G and start the AdbDriverInstaller.exe it will list your device and then press install.
Hope it Works !
*Note : *
It worked for me on Windows 7 but not on Windows 8
Edit
help me solve this issue on windows 8.1
Just go through the photos inside it for additional assistance go through this link
http://forum.xda-developers.com/showthread.php?t=2588979
All the best !