I'm troubleshooting a problem on a computer running Avast Free 2015, 10.4.2233. The computer is shutting down on a nightly basis. This is a normal windows shutdown, not an immediate power off such as what might be caused by heat.
Looking through the system logs, I found the following:
The process C:\Program Files\AVAST Software\Avast\AvastSvc.exe (HP-DC7900) has initiated the shutdown of computer HP-DC7900 on behalf of user NT AUTHORITY\SYSTEM for the following reason: Legacy API shutdown
Reason Code: 0x80070000
Shutdown Type: shutdown
Comment:
I found one thread here, fairly old that suggested it was doing this at the end of the scheduled scan. I've checked this, and there is no scheduled scan set up and the option is unchecked.
Does anybody know why Avast would do this, and how to stop it? The computer owner has already paid someone else, who couldn't figure it out, and I'd like to make sure she doesn't take it to someone else to look at (which will cost her more money).
Thanks in advance for any advice.

Eric the Grey