If you only want to view the contents of the file, you can use an embedded IE browser and set the document text to the file contents. This works for SGML, XML and HTML.
If you need special formatting of the file contents you can use XSLT to do the transform.
Unless you have a generic file structure, you will have to create an XSLT file for each structure.
It is a bit of a threashold to learn XSLT, but in the end it saves a lot of time in my experience.
XSLT Tutorial[
^]
Another option is to parse the document yourself, but that is a LOT of work especially if you have different file structures.