The XML plugin is installed properly in the plugins subdir and the 3 DLLs are copied to the Notepad EXE subdirectory.Other XML "validation" features work but there is no way to validate against an XSD.The validator checks for well formedness first, meaning that your XML file must be parsable using a DOM/SAX parser, and only then does it validate your XML against the XML Schema.
The Std In Parse utility can be used to call it from the command line.
Also, a commenter below points to this more complete wrapper utility.
This validator does not download any DTD or schema files, but relies on its own ones.
You can validate XML documents by URL, by file upload or by direct input.
Can someone explain how to use Notepad to validate an xml file against an xsd.
There are no options in the "XML Tools" plugin dropdown that provides for specifying an XSD file.
If the XSD is publicly available using HTTP and referenced through a "schema Location" or "no Namespace Schema Location", then the validator will pick it up and it doesn't need to be specified/uploaded.
*The maximum size limit for file upload is 2 megabytes.
Using the exact XML & XSD from this example worked and i realized what i was doing wrong.