Awesome work here, I have been looking all over the web for these kind of details.

But I was wondering if I could join the domain on a Ubuntu Desktop distribution instead of Windows XP using something maybe similar to Likewise Open or some other kind of LDAP client for Linux and still be able to make the OS authenticate against the LDAP when logging on to the normal Ubuntu Desktop GUI login screen.

Don't worry about GPO or the mapping of drives, just authenticating logon

Thanks... again good work