SMS2 on W2k Adv Server.

I’ve installed MS SMS2 server on w2k adv server. After that when I wanted to install SP3, it asks for SMSs-SP2, & when I tried to install SP2 of SMS it asks for some feature of SP1.

The problem is where can I find SMS2 SP1. I was not been able tofind it on MS site.

Could any one tell me where is the problem?
Where to find MS SMS2 SP2?
or Better what are the steps required for the successfull installation of SMS2 with its SPs on W2k adv server.