If you allowed changing attributes, I don't know what else/other ramifications might be.
There is little in the avast4 or sub folders that I can se a reason to backup other than the avast4.ini file if you have made any modifications to it. The other files would be recreated by installation. I don't back up any of my program files folder only volatile data files, which I can't recreate and don't want to lose.
I take an image back-up of my primary hard disk partitions every week as part of my system maintenance. This is saved to my second HDD or it can also be written to a DVD.
I also back-up volatile data files, .doc, .xls, etc. along with emails, bookmarks, address book, registration keys, downloaded files/programs, etc. (anything you don't want to lose) every day sometimes several times a day.