On 30 Jul 2016, Mort wrote in
alt.windows7.general:

My free Avast antivirus program showed that all 3 modes are turned
off yesterday. They cannot be turned on again. Avast troubleshoot
leads to a notice that a program is blocking my Avast; apparently
from "Avast.software.a.s." An Avast scan was clean. An
antispyware scan found 2 Trojans, which when deleted did not help.
Defender scan gave only an error message. Windows Malicious Tool
scan was clean. I deleted the Avast, then downloaded a new copy =
same problem. My smaller travel laptop is OK.

What can I do to find and delete the rogue program? If I am not
successful, then can anyone recommend another free antivirus
program, please.Many thanks.

There is no rogue problem. Apparently, Avast is blocking itself, or at
least appears to be. The most recent update of Avast had some severe
problems. There has been some heated discussion of it at the Avast
forums. Supposedly the problem was fixed in an update from today. Try
running another update.

Maybe there are some more solutions found in these topics:

https://forum.avast.com/index.php?topic=189194.0

https://forum.avast.com/index.php?topic=189221.0