Today we have GOOGLE 
here:
http://www.simplysup.com/
I've had TR (Trojan Remover) on my PC for many years. It works well with Avast.
Although I don't use it all that often, I have a life-time license so keep it updated. About 5 years ago when I was a McAfee user, I got an infection of 'Bad-Trans' Trojan through an email. (This is when BadTrans first came out). McAfee didn't handle it right back then. McAfee thought called it a PWS (pass word stealer) with different characteristics. All or most of the AVs now handle BadTrans just fine. I tried TR on a free trial basis to see if it could get rid of BadTrans.
It did!! It detected it, rebooted my PC into safe mode all by itself and removed any necessary registry items. Since it fixed my PC I bought a life-time license (was only $20 then, now $34 I think).
So it does work with avast. TR is an 'on-demand' scanner only, but can be run at startup if so desired.