Is your dad running a hardware based router? If so remove Norton Firewall and turn off the XP Firewall. The hardware based router will do more than both of those and if you have the XP based (Sp2) firewall installed IT will conflict with Norton.

Also get rid of McAfee, those commercial programs never do you really any good and you will fight with them more than not, as in another post I said go get a great free one called avast; http://www.avast.com