Tried to do the update, also tried installing latest version.
Got the attached error message.
I am using Windows 10 64 bit on this desktop PC.
Works OK on my Laptop running Windows 10 32 bit.
Cheers
Gerry
Download the avast uninstall utility
Uninstall avast via add/remove and follow the instructions.
Run the avast uninstall utility in normal mode and the tool will ask that this tool will run your computer in safe mode automatically click yes and follow the instructions.
Install a fresh new copy of avast and after installation is complete it will run a quick start up scan. Once finished restart your computer manually and register your copy of avast.