Is XP Firewall Good Enough for Business

I am about to be working on a small business network currently consisting of Windows XP PCs. They have Symantec AntiVirus and Windows XP Firewall.

I’m not a big fan of Symantec/Norton, but at least it’s something. The main thing I am worried about is the lack of 3rd party firewall. Is the Windows XP Firewall good enough for a small business? Or is it useless (dangerous) enough that I should attempt to convince the powers that be to invest in a third party firewall, such as ZoneAlarm?

Any help is greatly appreciated.