Microsoft Windows 2000 Professional, Server, and Advanced Server were Common Criteria certified in 2002. The Security Target, Validation Report, and certificate are available here:

http://www.niap-ccevs.org/cc-scheme/st/vid4002/

Although mainstream support for Windows 2000 retired in 2005, extended support continues to mid-2010. We can also reasonably expect self-help via online support to continue past 2010.

Here are the details of the Windows 2000 Professional support lifecycle:

http://support.microsoft.com/lifecycle/?p1=3071

And this is an overview of the Microsoft Support Lifecycle:

http://support.microsoft.com/?LN=en-us&pr=lifecycle