Hi Again.
OK, I think I found the answer.
On the System Properties screen, System Protection tab, there is a Configure button.
You can select it for each drive you have on your computer from the list above it.
I have system protection turned off for drives D:, E:, and F:, and it's turned on for Drive C:\.
You can set how much space is allotted, for storage of restore points.
Mine was set to 1%.
I'm guessing that, that isn't enough so I changed it to 10% for now, I have a lot of free space on drive C: so I won't miss it.
I'll try it for a while and see if that fixes the problem.
Mike