Some people have ended up on this blog after a Google search on Microsoft XML Parser version 5.0 - used in my XML Parser sniffer. There is not much info about this version on MSDN or on other sites. The main reason for this is that the 5.0 version is not made available for public download or independent release. It is only available with Microsoft Office 2003. That means that many people have the 5.0 version. I am not sure why Microsoft have decided to do this, they could have included it in an IE update or the Service Pack 2 for Windows XP. That said, it should be noted that there are not many changes in the 5.0 version, while the earlier upgrades have included major changes and improvements.
What's New in MSXML 5.0
XML Digital Signature
Validation of DOM nodes
Import DOM nodes
Additional second-level DOM properties
* Modified support for handling inline schemas