I have installed a Russian version of avast! 4.1.418, but it is quite ugly and hardly readable, so I decided to add the English language support. But where do I find the language packs for avast!, and are they available at all? I wouldn’t like to download the complete English version just to get the English user interface.
Have you read Avast’s website?
I gues not. Have a look HERE.
Cheers 
Ah, yes… I have looked at the Pro Edition’s main page, and I’ve searched through the forum, but I’ve completely forgotten about the FAQ. Sorry. :-\
Don’t worry. It can happen to all of us. 
Problem solved/answer given, that is what counts.
Actually, you can reach the same configuration dialog directly from the program settings / Language; there should be a link there saying “To install additional languages, click here”.