Networking with 2k server?

Thanks in advance.

When using Windows Explorer-Network/Workgroup....(to the server), I am
prompted for a username and password. I am getting a "login
unsuccessful: Windows is not able to log you on. Be sure that your
username and password are correct." The username and password are
correct and is a member of administrators group.

I am not running a domain and I did not have this problem with XP. I
have brought down the Windows Vista firewall and even stopped the service.

What am I missing?

Dave H.