Solved! Found the solution on YouTube.
https://www.youtube.com/watch?v=7Q4f9ezQ2j8
Download the online installer from Download.com
http://download.cnet.com/Avast-Free-Antivirus-2014/3000-2239_4-10019223.html?part=dl-85737&subj=dl&tag=button
When installing use “custom setting”.
Uncheck “Grime Fighter” not compatible with Windows 10.
He also unchecked “Browser Cleaner”. Update. I reinstalled Avast 2015 and did “NOT” uncheck “Browser Cleaner” and Avast still worked on Win10.
I also unchecked “Install Chrome”.
After doing this Avast 2015 is working on my Windows 10 64bit just great. At least on my machine.