Yes i had a same issue 2 i had 1 TB from EGO

it was disconnecting and reconnecting hole time.

I updated every thing and still didn’t solve.
My sisters 1 TB External Drive did work good on my USB.
So the problem was the 1 TB was not compatible with windows 8. So try a difference External drive.

If its still the same problem try this:

It could be the ur External drive that doesn't work but try first to update al your Hardware. (make sure you have downloaded the driver from ur External drive)
Look at your ASUS update programs if you have already updated everything.
You can update it by going to the website of ASUS and select your model and you can see if you have the latest drivers.

And the USB drive update I had was from the programme DRIVER GENIUS but diden't work but you can try.