Connot connect to the file server but can ping its IP.

We have this PX pro pc that we make as file server and before it was join to the Domain of the new server 2003 sp2 that we bought, it was working smoothly. But now we want o access still the XP file server but we cannot connect into it any more, i’am trying on pinging its IP address and it is responding.
Please help me with this it is possible that it has connection with the hardware, because when this XP file server was join to the domain booting up is taking soo much long longer than before.