A couple of days ago I asked BT to remove their Norton Security software and I installed Norton 360 which includes a small backup facility which I activated.
First of all, BT can't un-install the original Norton product only stop supplying possibly any service to it.
So it sounds like you have installed Norton 360 on top of the original Norton, which was not removed fully (as is the case with most Norton programs) and now you have 2 scheduled tasks set up but only one fully installed program.
If you take a look in Control panel > Task scheduler, then disable or remove the "original" task that was set up.