Whenever I try to start IIS, I get the error: The authentication service is unknown. I've searched Google, but all I can find relates to RPC (which is starting fine and runs using the local service account). I haven't uninstalled Client for Microsoft Networks, so that shouldn't be the issue either. I've checked Windows Updates and installed everything I can find. The only update that won't install is the latest Windows Installer. I've updated my anti-virus defs in the hopes that it might be a virus that I can clean off, but so far the AV scan hasn't turned anything up. I'm running Windows 2000 SP 4 with IIS 5. Any help is greatly appreciated.