I downloaded Avast again.

I uninstalled it from control panel again.

I used the uninstaller and took out ver 6, 5 and 4 in safe mode, in that order with auto restart and then system reboot between each.

Cleared temporary internet files.

Installed Avast latest version.

The definitions still won’t update. The error from the interface says invalid signature. The error from update via control panel says: there was an error when changing the system configuration.

Can anyone please help me?