Here (attached) is the log from ComboFix. A couple of caveats. When it was running before the restart, it threw up a series of error messages, such as the ones I'm attaching about various files, saying first that it couldn't back them up and then that it couldn't backup and then couldn't restore several files in the C:\Windows\System32 (or maybe they were all in C:\Windows\System32\config, I'm not sure.) There were a total of maybe 5 or 8 such files, with two error messages for each.
Also, when the system restarted and ComboFix came back up to finish its process, there was an instruction to not run any other programs while ComboFix was generating the log, but it was too late for that, as some program automatically come up on my system at startup, and I hadn't known to turn them off. One of the programs that started at that point was the Avast virus protection you had indicated I should disable. I did disable it (disabled all shields) but only until the "next startup" so it came up automatically after the startup. Please, let me know if I need to rerun ComboFix because of this.