access problem in LAN

There is a LAN which consists of about 20 computers. The OS of server is Win2003(domain control server), and each client is XP.
Only one of client computer has an access problem. That is this computer can't access the shared folder on server but can see it.
The server can ping this client and vice versa. Both by pinging hostname and IP address.

Who can show me the reason? Thanks a lot!

PS, How can I install NETBUI protocol under Winxp?

Maybe it's a security problem, a lack of permissions. I think the port required to see the folders and the port required to transfer information is different (as in, one uses the UDP protocol and the other is TCP). I'd check firewall settings too.

Thanks a lot, the problem has been resolved yet.