I prefer Norton Personal Firewall too. The Windows XP firewall causes too many problems for me, such as if I accept for it to be unblocked it asks me another 4 times!!!! This comcast I have never heard of it so I suppose it is for an ISP or maybe a product in another country.
I would buy Norton if you are considering purchasing another one.
If you have both the Windows Firewall and Comcast use comcast anythings better than Microsoft