Hello.
I recently had exactly the same problem with my iPhone 4S and, as you did, tried all the tips suggested, including deleting all Apple software on my Windows machine and reinstalling it and checking for updated drivers to no avail.
A friend suggested a different approach:
Connect you iPad
Close iTunes
Click Start
Click Devices and Printers
Right Click on "Apple iPad" in the Unspecificied Category
Choose Properties
Click the Hardware tab and the Properties
Click Change Settings and then click Uninstall
Disconnect you iPad
Restart you Windows machine
Open iTunes
Connect you iPad through a USB port
At this point the device and its drivers will be reinstalled.
It worked for me though, for whatever reason, I had to shift from one USB 2.0 port in the front of the PC to one of the USB 3.0 at the back as the drivers would not install on the USB 2.0 port. I am still looking into this as all ports on the PC work as intended (tested with another USB device).
Hope this will work for you as well.