Installation

This newbie is not sure if this is the right place to ask my question.
I have previously added Avast to another laptop. I am able to install to my PC, Winows XP, however get the following, “Unknown error the scan completed with error 42000= unknown error.” What is happening?

If you search the board for 42000 you should find some information.
Anyway, you can try to repair your installation:
Go to Control Panel > Add/Remove programs > avast! antivirus > Remove. Then choose Repair function in the popup window (Repair). You must be connected to the internet while repairing.