XP Network: Internet connection problems

Alright, this has been killing me so I hope someone can help me.

Right now I have 1 server running 2003 small business server, and 3 computer running XP pro. All of the computers can connect to each other and are "talking", but for some reason, one of them won't connect to anything on the internet. All of the other computers can connect to the internet so I am really confused on this one. I've done everything I could think of to get this to work but I've had no luck. Any help on how to the get this last one on the internet would be greatly appreciated.

Thanks

Nathaniel

 

How are the computers connected, and how are you connecting to the internet??

Are you using a router/hub to connect, and, for example, all the computers are connected to this hub, or is the hub seperate to the router/modem, and hence you are using, for example, Windows built-in "internet connection sharing" functionality?

 

running DHCP or hard set IP addresses.. ?
Checked the cable to the pc? tried a new cat5 cable?
can you see any of the other pc's on your network?
can you ping them?