Hello Mikaelrask,
To answer your questions, Avast! has one of highest false positive ratings in the industry according to the March 2015 edition of AV-Comparatives (an independent tester), and specifically the recent 150506-3 update sent out contained a huge number of false-positives that were reported as "Win32:Kryptik-PFA." The only scanner with higher false positives was Biadu. You are welcome to verify this yourself at
http://www.av-comparatives.org. As much as we both like Avast!, those are the facts.
Yes, I am sure the forced UI upgrade was because the older version was no longer supported, but in forcing the upgrade, Avast! forced me out of the game. The old machine cannot handle the bloat.
I already own Windows 7, and 8.1 on other machines, but I am software developer and I keep an older XP machine to support the older code I have written. Besides, I will not toss out an excellent computer just because Microsoft has dropped support.
Thank you for your reply and best wishes.
WindAndRain