Hi Thorn :
Like you, I have Win XP Home Edition ; however, my
firewall has not given me a similar "alert", so it appears
something was "using" Avast Web Scanner "name" .
If you click "Run", type "services.msc", click "OK" , what is
the "Startup Type" setting for "Avast Web Scanner" ?
Hopefully it is "Manual" . What firewall do you have ?