No internet connection on clients but there is on the server

I have a 2k3 box which is plugged directly into a router. This box is
the DC and runs DNS, DHCP, etc. The DHCP part of the router is
switched off.

I can connect wirelessly with a XP client and access all parts of the
network. However, I cannot get onto the internet. The server machine
has an internet connection (which is what I'm using to post this via
Remote Desktop) but none of the clients do, whether wired or wireless.

Does anybody have any ideas on how to get a connection to the client
machines? I have no proxy server or anything so it should be quite
simple.

Thank you.

D.