There are several possible reasons for this. The first is name resolution; XP is very fussy about accurate name resolution, so if you do not have DNS or WINS running locally, this will probably contribute to the problem. Make sure DNS is running and that the XP machine can access the DNS server. Also make sure XP's firewall is not turned on, and that the credentials for the XP machine on the NT machine are OK. Finally, make sure the XP machine does not have an empty password, as this can cause authentication problems.
This was first published in October 2003