The PC was purchased used with 7pro, and since it SEEMED to be a fresh install I did an in-place upgrade to 10pro instead of doing a clean install. My bad. I only ever installed an HP printer, Libre Office, and a few anti-virus tools, nothing I have not used before on several PCs. This PC seemed to work fine for awhile, but started to take a very long time to boot or to update, or to do anything, and might show 100% disk activity for an hour or more. Randomly I might get a "failed group policy login", or "failed windows notification service", or a windows boot manager screen with "File: \Boot\BCD, status: 0x00000c1?", IO error", but the very next boot might be clean. Even when reaching the desktop it might appear to be frozen or have very slow response for every activity, even taking a very long time to shut down. After a reboot or just waiting it out, it might return to normal, very responsive behavior.
I performed a number of scans with Malwarebytes, Defender, SuperAntiSpyware, SFC /scannnow, chkdsk, but no problems were ever found. Following suggestions I also tried turning off various optional features of 10pro said to be problematic. The slow behavior might go away for a day or two but always returned. For awhile I thought this was 10pro doing silent updates in the background, but this did not compare to the only other 10pro install I had access to. Aside from malware I thought I might have a failing HD or SATA cable, but a new cable did not fix it, and chkdsk / seatools scans never found an issue. On at least two occasions rebooting started some kind of automatic file system repair (probably due to hard resets) as if the HD was failing, but this would also finish with no repairs done, no errors found.
I did fix the problem completely by putting in a new HD and doing a clean install, but I still want to investigate the issue so I have reinstalled the old HD. At this point a clean install on the old HD would only tell me if the problem was SW or HW, without any clue about malware. Can someone walk me through the detection process on that old drive and maybe I will learn something?
Attached are the FRST logs.