Hardware Firewall for Small Business?

Hello Guys,
i need your help. I am working on a small business ( 1 server with OS windows server 2003, and 4 pc with Windows Xp). All the PC & Server have access on the internet.

All PC & Server have Nod 32 Antivirus (original).
Now i want to get a hardware firewall. .

Can you recommend something?

Do you have a router? I.e. cable modem - router - your computers? The router itself acts as a hardware router.


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