i desisnstalled and after,i had to perform a restore of xp system… so avast is back, but it is blocked and it’s impossible to remove it in the “add/delete application window”… When i try to reinstall from the complete setup, it says “remove old avast installation first” wich is impossible… what can i do ?
Download the avast! Uninstall Utility, find it here and save it to your HDD so you can find it later.
Run the Utility, reboot and install.
thanx a lot 
Your welcome.