in fact, VS2010 is "smart" enough that even if you close and reopen the file, it'll remember the values you've set in the Properties window. I've just started to learn xml, so i'm a beginner in this domain. Also be sure that there are not more references to the same schema.Open you XML file in VS2010; in the Properties tool window (F4) there is a Schemas property. Once done, the errors/warnings will show up in the Error List tool window.Now you need to have that Schema XSD Added into your Project.
See the documentation on the XML Editor in Visual Studio.While this article applies to Visual Studio 2005, it provides a graphical view of the capabilites that are present in 2005 and onwards.