Avast kills Vista PC

As Microsoft have started telling me that they won’t support Windows Defender any more, I decided to install Avast to take over. Went through the full routine, compatabilty checking etcetc, installed and ran, did a scan (ok); then noticed a couple of things: first, I can no longer fill in some online form boxes (could before, I did this morning before installing this poc); and then after shutting my machine down and restarting, all I get is a black screen… a quick check with Task Manager tells me that there is NO activity, so it looks like this has protected my machine by making it entirely inaccessible! I’m pretty unhappy about this, it’s my main work tool, and I’m using my wife’s laptop to try to find out what to do. Can anyone help?

Do you have an image of the OS-partition which you can reinstall?

Mainstream support for Vista ended 4 years ago.
Extended support will end in April this year.

Boot from a bootable medium.
Run Farbar and attach two log files to your next post (FRST.txt and Addition.txt)

nothing available to reboot with, and nothing to reinstall; I’m really unimpressed with Avast, a perfectly good & reliable machine killed.

Create or get a boot-able medium and use it.

Reliable with Vista on it ? HaHaHa