Do you have the new location C:\Program Files\AVAST Software\Avast as well as that old location avast5 location ?
Which may also have the reference to ALWIL Software . But I can't see the reason for having an \avast5\setup folder within the new folder layout, especially since you have done a clean install of avast 8.
So what is the full path to that location (as Eddy asked) not the ...\ path concatenation ?