I do not wish to be contrary but I have to wonder how long it will be in the interests of avast (or causing extra work to all in these forums) to go on supporting operating systems that are now way past their support date by the vendor of the operating system.
I have to doubt that avast derives any measurable part of its income from Win9x users and we are now at a point where even XP is, or will before long, cease as a marketed product. I hope that avast will continue to focus on its core users and not devote any unnecessary effort to unsupported operating systems. I do not want to suggest that, if it works stop it, but simply that support for those operating systems should be simply "as provided" and "please do not expect support".