You set maximum password age to 0
http://technet.microsoft.com/en-us/library/cc736566%28WS.10%29.aspx
Password policies are set at the domain level in Windows 2003 so it will be in one of your domain linked GPOs (some people use the default policy and others create their own...not sure how you are setup)
Why do you want passwords to never expire on the entire domain?
Thanks
Mike
