windows XP in a W2k domain

The users with admin rights can login with out any problems.

how did you add the users to the domain? Did you just add those users in the local security policy of the server under "access this computer from the network"? or use Active Directory? If your using W2K Server with Active Directory the user accounts you create in active directory should, at a minimum, be a member of the domain users group to allow domain logon.

Give us a little more detail on your W2K domain setup

Local user accounts will not have network rights available, you will need to have them login with domain accounts. This will set up new profiles for them on the PC and will give them only user rights. If you want them to have everything available as it was before the domain addition you will need to copy their profiles from the local accounts to the profiles for their network account. Be careful, while doing this you will need to give them rights to use that profile. You will also need to give their domain accounts the same rights to use the computer as they had before. I would also suggest disabling local accounts after you get it up and working for everyone to prevent them from logging on locally by accident. Even if the network is not available they will be able to log on with their cached credentials, so I would not recommend the use of local accounts (other than administrator) in a network environment.