I don't have SQL 2000 on my machine, but in SQL 2005 if you go to "Add/Remove Programs" under "Control Panel" and click on the "Show Updates" checkbox, it should show the latest service pack applied under "Microsoft SQL Server." It does this for SQL 2005 at least. Remember that you have to do this on the actual server, not on a client machine. Also, I think you can do a help --> about in Query Analyzer or Enterprise Manager. You'd have to check though.
What OS are you using? This example worked under XP and Server 2003.
I hope that helps!
Brett
--------------------------
My new website coming soon!