I'm currently trying this:
using DocumentFormat.OpenXml.Packaging;
using (WordprocessingDocument wordDoc = WordprocessingDocument.Open(fileNameDocx as string, true))
{
      var xdoc = wordDoc.MainDocumentPart;
      mainWebBrowser.NavigateToString(xdoc.Document.OuterXml.ToString());
} 
But this just gives me the text and none of the formatting. Is it possible to show a ".docx" in a webbrowser control like this?