well you might want to make your question a little more clear, but i'm guessing you want to join your Linux box to a Active Directory domain?
there are two ways this can be done.
1st. Joining the windows domain
http://www.yourhowto.org/content/view/31/9/ - (change the /etc/pam.d/pop3 to /etc/pam.d/login or whatever pam module you want)
Or
2nd. you can Authenticate using Active directories LDAP
http://www.yourhowto.org/content/view/34/9/
I hope thats the answer to your question and it helps you