found this in the help for pro version, but I'm not sure if it's what you're talking about.....
Explorer Extension - ashQuick Program
ashQuick program is, just like avast! and ashCmd, a scanner for viruses. It is usually used to scan files from the local context menu, e.g. from Explorer. In other cases, it is better to use avast! or ashCmd.
Setting up the Explorer extension
The Explorer extension settings can be modified directly by editing the "Explorer extension" task. Additional settings can be found directly in the Settings of avast! program.
Note: To be able to edit the "Explorer Extension" task, you have to enable showing the special tasks in the avast! settings (on the "Enhanced interface" page).