Finding which clients are connected to my active directory

Hi all,
I m using Windows 2003 Server with service pack 2 and active directory installed on it.
Problem is that we can find only those users who are connected through thin clients with my server.

I want to know that how many users are connected with my server whether they are from thin client and from clients/workstation.

Can any one help me that how can i find users who are working on workstations?