The basic ashQuick.exe doesn't scan memory, unless you run it from a command and have parameters, I can't remember the parameters, Tech probably has them filed away somewhere
In the home version you haven't got a GUI means of firing the anti-rootkit scan but it can be done by a run command, I can remember that
avast! Rootkit Scan - Windows Start, Run and copy and paste this command (including the quotes, assumes that you installed avast in the default location) "C:\Program Files\Alwil Software\Avast4\ashQuick.exe" "<RTK>SUPERQUICK" and click OK.