WinXP SP2, Firewall, ISP Not Connecting

I have just installed the SP2 on my Windows XP. Right after that was done I haven?t been able to connect to the internet. I would have to first disable the windows firewall to connect and then enable the firewall again. My question is what should the default or normal settings be for the firewall, what would be the correct settings so that I can connect normally.

Specs: Windows Home Edition XP
Upgrade: SP2