hi,
A driver is software that actually runs the hardware (network card) and tells the operating system (Win8) what to do, how to do it, and AIS would have to work within these constraints to set up and initiate and run the firewall part of AIS. If this part of AIS setup fails, then you will get the errors you have had.
So, one possible solution here is to get a network card driver specifically made for this card compatible for Win8. Since Win8 is so new, might be a bit of time before the vendor of your card provides such a new driver. OR, as Avast! has just become compatible with Win8, this could be an issue that originates with AIS, as your card may or may not be a common one; it may not even be in the Avast! setup database.
Hard to tell from here.
So, a solution to consider is to either get a newer driver for Win 8, while still using your original network card, with it matching the new requirements above, or replace the network card with a new one, and a driver known to be compatible with Win8. I am not saying this would definitely work here, it might, is all I can proffer here.
Not sure if this might even be worth considering, as it does involve a bit of work with no certain guarantee, and you do now have a setup that is working for you.
Avast! team member pk seems good with these sort of issues, thinking about asking him or someone similar to come in and assist you. pk actually works for Avast!, just so you know.
As for the file Windows.old being present, that is proper.
You have an upgrade disk (Win8) that required Vista to be installed in order for the upgrade to happen and successfully complete. Windows.old is the original windows installation left behind when the os is upgraded. No worries there at all about this one.