Fix Ipad and Ipad 2 “Not Charging” error, while connected to PC USB port. Asus Ai Charger DL LINK: event.asus.com .This fixed my problem on my Dell, and it works great, it works on many computer and many motherboards. I do not guarantee that it will help you but it did help many people, it usually works. This will also charge your other USB devices twice as fast, because it doubles your amps from 500mA to 1amp. GoodLuck!
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Fix iPad 2 "Not Charging" While Connected To PC USB (also charge your other apple idevices faster)