NIS Continuously WRiting to Hard Disk

After 15 minutes, or so, after boot-up, NIS begins doing continuous writing to my hard drive. It is not reading. Only writing. If I turn on silent mode, the writing stops. It is not light writing, but 100% disc usage, all writing.

This problem has trashed one hard drive already. I have to remember to turn on silent mode, every time I boot my PCs. Yes. It is happening on two very different machines, running different versions of NIS. Silent mode stops it on both machines. I see someone describing a similar problem on a Win-10 machine, and had experienced it on a Win 8.1 machine.

I have run the Norton tasks window, and during writing, there is no task being shown as running.

What could NIS possibly be doing that requires such writing?

Please help. It has been happening for over a month, on both machines.

One machine is an XP-Pro machine, running NIS version 21.7.0.11. All virus definitions are current.

My other machine is a Win-7 Pro machine, running NIS version 22.9.4.8. All virus definitions are current.

Rich P