Logon Credentials were incorrect - asks over and over

I have two computers on which I am installing Outlook 2000 on a W2K PC, using an NT 4.0 server with Exchange 5.5, that will not authenticate the NT user for Outlook. It keeps coming up over and over with the username, domain, password screen when you go to log on to Outlook. The user's information does not work. The 'check name' box will not resolve the user name on either of the PCs either and they are different user names...get CANNOT RESOLVE NAME message. I am up to current service packs on all. I tried MS's suggestion regarding the ClientProtocols in the registry and they are fine. I also uninstalled TCP/IP and reinstalled it after a reboot. Any suggestions as to how to get these user's mailboxes up? Very frustrated with this. Thanks for any help!

FYI .... I figured out what the problem was. The last time the server was rebooted, the WINS did not start up properly. After looking at the Event Viewer and seeing this, I rebooted the server and the WINS started up and the user can now log on with no logon credentials needed.