McAssey said:
. But then once again I noticed that the System file was requiring more and more memory, driving my total memory use up to more than 90% of my 4.0 GB of memory available, resulting in constant swapping of data to the disk and slowing my system down once again to a crawl. Here is a screen shot right after booting up.

As you can see, the System file is killing my system.
Hi, two observations:
1. The largest user of RAM listed by the task manager on mine (nominally 4Gb laptop) is "System and compressed memory" at 224Mb.
I don't see that on your screenshot at all. It's new in Win 10.

From one of the articles below, are you using an older version of Win 10? ('System' renamed to "System and compressed memory")
2. Why is Windows Defender working so hard? Look at its disk use.
I gave up on that almost immediately as it was using lots of CPU for no apparent reason - when I was struggling to get my CPU use down to below 10% after upgrading. (No such issue on a clean install, tho').

It's worth understanding a bit more about how RAM is managed in Win 10:
Why Is Windows 10 Process Using So Much RAM?
Memory Compression in Windows 10