The TBB library itself should work fine on Windows 2000, provided that the proper version of MSVC runtime is accessible. All Windows API functions explicitly used in TBB are available in Windows 2000. Officially, however, Windows 2000 is not supported and we do not test TBB there.
I assume you probably have some testboxes running Windows 2000; if so, you could try running TBB examples (might be even tests) there and see if there are outstanding issues seen right away. If any, we would of courseinvestigate those.