Are you on a homegroup by any chance?
I've read some MS answers that flat out say that the archive bit is no longer available in windows 7 (but I think they mean reliably usable rather than not available in the strict sense). To others saying that the homegroup networking is using it for it's own purposes (probably for it's own built in backup) and it interferes with other people/programs using it.
Personally I have not looked into it though.
I believe that the base "dos" attributes are the same as always though: Read Only, Archive, Hidden and System. Of course NTFS itself has (and has always had) a much more extensive access control system in place for all folders and files...