Background noise is correct. It's very important to run this tool after Norton is removed by first turning it off (disable) then using add/remove programs, as what's left over can interfere with aspects of other security programs, including Windows own security centre.
Make sure you're disconnected from the net during this uninstall, download AVG to a folder location first before uninstalling Norton. Run the uninstall, then the removal tool, reboot as prompted (and if not, reboot anyway) then install AVG, then reconnect and update it.