I have used Avast home/free for years and decided it was time to buy AIS and give something back. I'm very impressed so far. I had zero problems upgrading from Avast 5 free to AIS on my three Windows 7 64 bit PC's. Made the purchase got my license and had the first PC registered and updated to AIS in under 10 minutes. The upgrade process was smooth as silk. It could not have been easier. I can't wait until 5.1 comes out!
Bill