Must be an admin to logon to network?!

Hi,
I started working at a new company and I am having some problems. One problem is all users must have administrative rights to logon to the domain. I have never heard of this and if I take them out of the administrators group I can’t sign on. Second, when logging on no one has the rights to change their passwords. If I set Windows to have the passwords expire the users can’t change them, even though they are in the administrator group. This is an NT server. Any help would be appreciated. Thank you.