Sorry folks - I have to agree with Mac.
Nearly 90 percent of XP pressings whether retail or oem for the trade have never been updated or patched - not even once. You all know with absolute certainty that XP contains the code to establish this with total accuracy don't you?
Now use your skill and judgement to estimate what percentage of that 80+% will have installed third party software firewalls and the nano percentage going for a hardware firewall
I've said it before and I promise it is without any sneering you are entirely unrepresentative of computer users.
Regards
Rob