Installing Nexus 4 ADB drivers on Windows 7 x64.

Having trouble installing the ADB drivers for your Google/LG Nexus 4?

After much trial and error, I found a solution that worked for me, as of 08 May 2013 with Jelly Bean 4.2.2.

First, use the Nexus 4 Toolkit to install the ADB driver. It also comes with tools to root and backup your phone if you so desire.
http://forum.xda-developers.com/showthread.php?t=1995688

Alternatively, if you only want to install the driver, you can go directly to Koush's universal ADB driver, which the Nexus 4 Toolkit uses.
https://plus.google.com/103583939320326217147/posts/BQ5iYJEaaEH

I had trouble trying to install the default Google ADB drivers that came with the Android SDK. For some reason, I guess the driver is not signed and the 64-bit version of Win7 refuses to install unsigned drivers. Oh well.

Next, make sure your ANDROID_SDK_HOME environmental variable is set correctly. I had installed an earlier version of the Android SDK, so mine was pointing to the wrong location.

It should point to where your .android directory is located - usually c:\Users\[YOUR_USERNAME]\.android

Set the environmental variable by right-clicking on "Computer" and selecting properties > Advanced System Settings > Environmental Variables.

You may also want to add the platform-tools directory to your PATH so that you can run ADB from any location in your command prompt.

Next, restart the ADB server by typing "adb kill-server" followed by "adb start-server".

On your device, you should have the Developer options > USB debugging turned on. If you don't have the Developer options enabled, you can do so by going to Settings > About phone and then tapping on Build number seven times.

If all goes well, you should see a pop-up on your Nexus 4 asking you if you want to accept connections from your computer. This is a new security feature in Jelly Bean 4.2.2 and you'll have to accept the device fingerprint if you want adb to work.

There you go! Have fun with your adb-enabled Android device!