virus and False Positive problems should be posted in the viruses and worms forum section

and in that section you find this guide…

follow instructions and attach logs (not copy and paste) http://forum.avast.com/index.php?topic=53253.0

run in order listed
AdwCleaner / Malwarebytes / OTL / aswMBR

when done, removal experts will be notified and help you
when finish, all tools used will be removed

you may also attach a screenshot of the avast warning popup