Microsoft Software Update Services (SUS)

Hi, We have NT 4.0 domain setup & face problems of installing & patching up all client systems (Win9x, 2K, 2003, XP) so we installed Microsoft’s Software Update Services system on a Windows 2000 Server.
Now I downloaded all patches on the SUS & approved them as well.
How do I get them to be installed on client systems ? The SUS Client does not get installed on Win 2000 Pro SP3 & above systems.
Anyone worked on SUS ??
Please get back & email me at akasheep_b@yahoo.com
Akash