DNS problem

Hi all, I work at a helpdesk in the U.S. Army and am having a problem. Whenever I try and add a certain computer to the domain, it says there is a DNS lookup problem. The website they directed me to was all server related. To troubleshoot I checked same settings on another computer using the same OS (Windows 2000 Pro) the computer connected on the domain on the second computer. I tried another computer name for the computer giving me problems and recieved same error. Does anyone have any suggestions on why this 1 computer can’t locate Domain when all other computers on same network and using same OS can?