common problem. Usually happens if you aren't logged on as the exact same user on both machines. My way around that was to to allow anonymous logon on the w2k box. First go to "local security policy" under "computer management". Then under Local Policies/User Rights assignment/Access this computer from the network. Just add Anonymous logon to this key.
2nd, the built in guest account was enabled, and 3rd allow anonymous user access to each share you want to access this way.
Or log on to every machine with the same name/pass. Both ways work.