Anyway, the short version of my discovery is that I found that I have either a bad SD card (which I usually keep in the SD card slot) or perhaps a problem with the built-in SD card reader in my M4. In any case, I removed the card and now my system zips along.
Apparently, as best as I can tell, the corrupt card (or reader) created a problem for windows explorer as each file operation causes explorer to consider all available devices, resulting in a significant delay when a device does not respond properly.
I don't think that this is the cause of all of my slow-down problems, but I now believe it's at least a major player.
Has anyone experienced this?