Avast Update

Avast just popped up a window - insisting I let it do an update.
So I did.

Then Avast wanted to reboot, so I allowed it to.

When my computer had finished rebooting, my “Philips” monitor was removed as the default monitor and my resolution was dropped from 1600 x 1200 down to 1024 x 768.
Of course - all my Icons on my desktop were all rearranged alphabetically starting at the top left, downwards.

Plus - I keep getting the almost “stealth” install of Google toolbar.
If I really wanted the Google toolbar, I would already have it in place.

What is it in the update process that persists in nuking
my monitor settings and my desktop layout?

Thank you

John