SQL Server 2000 Service Pack 4 (SP4) adds platform support for Microsoft Windows Server 2003 x64 Edition, allowing 32-bit SQL Server 2000 applications to run on 64-bit platforms using the Windows on Windows emulator (WOW64). SP4 addresses specific issues discovered in SQL Server 2000 since its ship date. SP4 is also the first service pack to service the 64-bit edition of SQL Server.
Because SQL Server service packs are cumulative, SP4 includes all fixes from previously released Service Pack 1 (SP1), Service Pack 2 (SP2), Service Pack 3 (SP3), and Service Pack 3a (SP3a). SP4 can be applied to an original SQL Server 2000 installation or to one where SP1, SP2, SP3, or SP3a was previously applied.
The article continues at http://www.microsoft.com/sql/downloads/2000/sp4.asp