Windows passwords

We have our users logging into a NT server. We want them to be able to change passwords every three months for security reasons. The problem we have run into is that when we change their NT password and they log in, then the Windows password box comes up, because they have a different password. I do not want to have to go around and clear all pwl files off each workstation to prevent the Windows password box from coming up. Is there a way to disable the Windows password box altogether. I have some workstations that are running Win95 and some running Win98. Any suggestion would be helpful

Thanks,

ATurner