Jumping back to my last post.... I may have made some progress in my freezing issues.
If you recall, my Windows 7 system would freeze up after being idle for any length of time. I could move the mouse - but do nothing with it. No key combinations would work either. The hard drive activity light would blink regularly but not actually do anything. Eventually the system would start responding again. Sometimes after a couple minutes, sometimes after 20 minutes.
I might have made some progress. Since posting that message I've disabled Windows Defender (because it is awful and I don't need it anyway) and have disabled the EFS service. Since then, everything seems OK so far - but this is really a day to day problem so while it might appear to be resolved now, it may return tonight or tomorrow.