If your Android 4.3 Nexus device does not show on your PC...

[tr00don]

Try (re)installing the OEM USB driver from the manufaturer, not from Google: LG for Nexus 4 and ASUS for Nexus 7. With the Google USB driver your Nexus may or may not be listed as a storage device in Windows Explorer under Computer, but in USB debugging mode (used by developers) it may disappear altogether.

 

[pkcable]

Thanks for the heads up!