How do I open an XML file as Western European, not as UTF-8?

Open Tools | Properties for Current Configuration, and open the File page. Change the Opening Encoding to your choice.

Configuration File

If Detect HTML/XML Charset check box is checked, a encoding= directive specified within an XML file is searched, and EmEditor uses the specified encoding if the directive is found. Note that the encoding specified for opening files is different from the encoding specified for new files or for saving files.