Cant back up to external usb-3 Toshiba drive

I bought a Toshiba hdtc710xr3a1 external drive for backing up my new
computer running professional windows-7 64 bit operating system.. I
also bought Acronis True Image 2015. This a home-built desktop.
computer.

Repeated attempts to back up using Acronis failed, apparently blocked
by the external drive.

Failing with Acronis, I attempted to backup using windows' program,
which also failed.

During all this, pop-ups asking how I wanted to use the drive
repeatedly appeared. Also, I kept getting pop-ups saying I needed to
format the drive before I could use it. It is already formatted.

To insure the drive could accept files, using explorer I copied
several files to it from other hard drives. And then deleted them.

So, to make sure the backup programs were functioning correctly, I
successfully backed up, using both programs, to a empty/spare internal
hard rive. At lest I have a backup now, but not where I wanted
it/them!

The drive had backup software installed on it, which I didn't want to
use.

So, it appears that there is something unique about the drive that
windows doesn't like. I am about ready to return it. I hate to,
because I like to solve problems...not skirt them. This is a new
experience for me.

I have successfully used a Toshiba external drive (different model) on
my laptop.

Before I ship it back, I would like some comments on this problem.

Ben

Long time lurker, first time poster here.