What is the difference between XMLHTTP and ServerXMLHTTP?
XMLHTTP is designed for client applications and relies on URLMon, which is built upon Microsoft Win32 Internet (WinInet).
ServerXMLHTTP is designed for server applications and relies on a new HTTP client stack, WinHTTP.
ServerXMLHTTP offers reliability and security and is server-safe. For more information, see the MSXML Software Development Kit (SDK) documentation.
taken from http://support.microsoft.com/default.aspx?scid=http://support.microsoft.com:80/support/kb/articles/Q290/7/61.ASP&NoWebContent=1
