NT Server DHCP Problem…

I am consulting for a small site that has a Dell Server that was previously built with NT Server. This server has always been set with a static IP, with the workstations receiving IP’s from DHCP. I was installing a DSL network and the server would not allow me to change the settings to obtain IP from a DHCP server, even after logging in locally under an admin id. After setting up the router, the workstations work great(on the network and receive IP’s like they are suppose to and can surf very nicely), but the server does not see the router at all. I tried to ping it but no resonse. Any help will be greatly appreciated.