If you use Notepad++, I would suggest installing the XML Tools plugin. You can beautify any XML content (indentation and line breaks) or linarize it. Also you can (auto-)validate your file and apply XSL transformation to it.
Download the latest zip and copy the extracted DLL to the plugins directory of your Notepad++ installation. Also, download the External libs and copy them to your %SystemRoot%\system32\ directory.