Good luck with reverting to an older version because you’ll need to completely uninstall your existing Avast installation for it not update back to v.8.
I recently had problems with getting rid of the pro-trial version which just appeared after an update and I had NEVER agreed too. I have Avast v.7 (whose GUI I very much prefer) from a UK PC magazine cover disc so I decided to reinstall from that. I used Revo Uninstaller on the existing Avast installation and thought I’d got rid of it. Installed the more pleasing looking v.7 OK but on checking it I discovered all the shields were down and refused to be activated. I got an error message saying certain key files couldn’t be initialised.
Using my knowledge from previous Avast troubles I used the repair tool (and why isn’t that and an uninstall option provided as part of the Start Menu Avast shortcut like most programs?) and that fixed it. But when I relaunched Avast Free, now restored and working 100% I discovered that it had reverted back to v.8. Clearly the Revo uninstall had left something of the old installation behind.
Apparently to get rid of it completely you need the special Avast provided unistaller tool. I was so happy getting rid of the pro-trial version I didn’t want to stuff things up again so I left it at that.
I hate software that is difficult to uninstall with a passion.
Point is reverting back to an older Avast version isn’t as simple as it might seem.