I quote Knowledge Base article Q260910 - How to Obtain the Latest Windows 2000 Service Pack.

SUMMARY

Service packs are the means by which Windows 2000 bug fixes are distributed. Service packs keep the product current. Service packs include updates, system administration tools, drivers, and additional components. All are conveniently bundled for easy downloading. Service packs are cumulative; each new service pack contains all the fixes that are in previous service packs, as well as any new fixes. You do not need to install a previous service pack before you install the latest one.

Windows 2000 service packs are for Windows 2000 Professional, Windows 2000 Server, and Windows 2000 Advanced Server.


MORE INFORMATION

Windows 2000 Service Pack 1

Windows 2000 Service Pack 1 is the first service pack for Windows 2000. Service Pack 1 will be posted to the following Microsoft web site on Monday, July 31, 2000:
http://www.microsoft.com/windows2000/downloads/recommended/SP1
For additional information about the problems fixed by Windows 2000 Service Pack 1, click the article numbers below to view the articles in the Microsoft Knowledge Base:
Q259524 List of Bugs Fixed in Windows 2000 Service Pack 1 (1 of 3)
Q269425 List of Bugs Fixed in Windows 2000 Service Pack 1 (2 of 3)
Q269428 List of Bugs Fixed in Windows 2000 Service Pack 1 (3 of 3)