annoying window in google chrome with avast 2014

I have installed avast 2010 and now, each time I open google chrome, it appears a second window in my browser. This window says “thanks for installing avast online swecurity” and invites me to download avast mobile security. I close the windows, but each time I open chrome it appears again. How can I di to remove this annoying problem?

How can I di to remove this annoying problem?
in chrome settings

http://lmgtfy.com/?q=Stop+Chrome+Loading+2+Tabs+at+Startup

please tell me what I have to do in chrome settings,because I can’t find a solution and I am tired to see this annoying advertisement avast page!