This tool has been discussed many times already. Please use the Search feature before posting new questions.

Here’s some of the relevant threads:

http://forum.avast.com/index.php?board=2;action=display;threadid=4979;start=msg36041#msg36041
http://forum.avast.com/index.php?board=2%3Baction=display%3Bthreadid=778%3B

Thanks
vlk