B Trevathan, Spybot 2.0 beta 1 isn't quite stable enough to use under Win2000. which is why i believe installation is not supported under win2k. there are still several problems found with the current beta release of Spybot S&D 2.0.

you may want to wait for a more stable release of it; perhaps when Spybot 2.0 reaches either release candidate or final release which should support win2000 by then.

otherwise, consider using other anti-spyware tools like SUPERAntispyware, Malwarebytes Anti-malware or Lavasoft Ad-aware; the latest versions of these 3 tools still work under Win2000.