CANNOT JOIN DOMAIN ?

I INSTALLED WINDOWS 2000 PROFESSIONAL ON MY LABTOP AND IT WENT VERY WELL, HOWEVER I CANNOT JOIN MY DOMAIN AT WORK, IT KEEPS SAYING CANNOT CONTACT DOMAIN OR THE DOMAIN DOESNT EXIST. THE REST OF THE NETWORK IS RUNNING EITHER NT 3.51 OR 4.O THE PDC IS RUNNING ON 3.51. I CAN PING THE PDC AND EVERYTHING ELSE, I WOULD APPRECIATE ANY SUGGESTIONS THANKS IN ADVANCE TOM