NS, Win10, over 90% disk activity makes using PC 'hard'

We've got NS on 2 PC's, both Dells that were upgraded from W8.1 Pro to W10 Pro. An XPS 8500 (Intel i7-3770 CPU, ATI HD7000 video, boot from SSD and 2 hard drives) and a XPS 435T (Intel i7-920, ATI HD7770 video, boot from SSD and 2 hard drives).

The XPS 8500 appears to work fine.

However, not the XPS 435T. NS seems to be 'eating' up the disk access on the last hard disk, see attachment 1.

Live Update says all is up to date? Trying to do simple tasks, like start Task Manager takes forever it seems.

If I open NS or look at the icon on the SYSTRAY it doesn't show ANY scan running. However Resource Manager shows it is ACCESSING my IPAD backups?

Wouldn't a BACKGROUND scan show as scanning?

Suggestions. BTW, the 8500 also has an IPAD backup and it isn't happening on that PC?