My WinXP Avast stopped working

Avast suddenly came up with the “cannot start UI” message on XP and Win10.
I followed the (different) recovery procedures, successful on Win10, but not on XP.
Uninstalled (last resort) and re-installed, now Avast doesn’t even try to start, let alone give an error message.
It shows as installed in the Add/Remove Programs list, and goes through the “repair” process without error.
I re-booted in all the required places.

What can I do ?

There is some information here. :slight_smile:
https://forum.avast.com/index.php?topic=219361.0