Hi Vishal,
If you don't want to use windows at all, you can setup a server
with Samba using LDAP as the backend. This allows you to replace
a PDC and have unix/windows logins both to the same OpenLDAP
database. See the HOWTO at:
http://samba.idealx.org/
Also there is a very good book on OpenLDAP which has just been
published by O'Reilly. See
http://www.oreilly.com/catalog/ldapsa/
This covers (about 4 pages) howto set up LDAP/Samba for windows
authentication.
If you *must* use ADS, or keep a Windows PDC, then I have some
patches for OpenLDAP that will allow you to store all your attributes
uid,gid,homedirectory etc in OpenLDAP, but just passthru the password
authentication to a windows PDC. It's a patch for OpenLDAP 2.1.6
Paul