Avast won't install

the message keeps popping up: remove Sophos - I’ve done that yet Avast keeps telling me to remove it??? I am getting frustrated, any help :-[

Be sure to get rid of all remnants of your prior installed AV(s)…!!
https://www.avast.com/faq.php?article=AVKB11#artTitle

The problem is that when you remove something through control panel almost never the application is removed completely.
It leaves traces of the application behind, and that is what avast is detecting.
Removing the application (in this case Sophos) completely will solve the problem.

How to Successfully Install Avast http://goo.gl/VLXde