XP 2 unable to contact domain controller

I am trying add an XP SP2 workstation to an existing network but am having problems getting the XP to join the domain. Error “domain controller for the domain xxxxxx could not be contacted? I am able to ping the domain controller’s and gateway’s IP addresses but cannot ping the workstation from the DC. I am logged on as the PC admin. I tried both static and DHCP IP addresses for the workstation and have turned the firewall off. What am I missing? Please help