If you are worry about your system might be infected, Follow this guide: http://forum.avast.com/index.php?topic=53253.0
Open a new topic and attach ( Do not copy/paste ) logs for Malwarebytes ( MBAM ), Farbar Recovery Scan Tool ( FRST ), and aswMBR.exe ( you find these programs in the guide above ) here:
http://forum.avast.com/index.php?board=4.0
Where an expert in the removal of malware will help you.
Avast is set up as default to give you the best protection and best performance to run in your system. Any settings you change will give different results, and the user must be awared and prepared for. Better to read the manual or faq before you change anything. You can also click on the upper ? symbol to your right on any Avast window you open to learn how things work.