Windows 2003 DOMAIN NAME

How do name my domain? I have a Windows 2003 STD server with 5 XP machines 1 printer 1 firewall. Can someone tell me how to name my domain. I’m struggling between “companyname.local” and “companyname.com”. I’m not hosting my email (exchange server) or the website at this location. No plans of bringing them in house in the near future. I just wanna be prepared for adding other servers in the future. Is there a way to chose the right name for your name. PLEASE HELP!!. Thanks in advance.