Well hidden away in the windows setup, under iis and web services...an option to serve SSI
http://www.microsoft.com/resources/documentation/WindowsServ/2003/standard/proddocs/en-us/Default.asp?url=/resources/documentation/windowsserv/2003/standard/proddocs/en-us/gs_installingiis.asp
do a search for shtml on that page....