The Norton ubervirus could certainly bollix an in-place Upgrade which is why they tell you to shut it down.
Since you have that insidious virus and it is impossible to remove without damaging system files anyway, I suggest you boot from disk, delete all partitions, create new ones as you wish, then format and install to first partition.
Afterwards download free Avast Home which is featherlight and, after it's initial boot scan, will let nothing bad in unless you turn it off.