IIS 6.0 is the version available on Windows Server 2003 computers and (like on Windows XP) is not installed by default.
If you have IIS 6.0 installed on a Windows Server 2003 computer without Service Pack 1 (which you should apply as soon as possible), these are the patches that you need to apply to your computer:
MS04-030 : Vulnerability in WebDav XML Message Handler Could Lead to a Denial of Service (824151)