"The SP2 installation simply uses the previous configuration of the firewall:"
I think that explains it nicely. If you had this shared before, and had it setup to allow such, then it DOES WHAT YOU ASKED.
If you thought you was secure think again. Dont know if its true but I thought others would like a read.
My question is, is this just a problem for users running the windows firewall or for users running a third party firewall also?