You can download sp4 here.
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. SQL Server 2000 SP4: Includes a new version of MSXML version 3.0 SP6. With SP4, the OPENXML statement is updated to use a custom-built XML parsing technology designed to be backward compatible with MSXML 2.6. Includes MDAC 2.8 SP1 except for Windows XP and Windows Server 2003 platforms, where it is included with the operating system service packs for those platforms.
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.