Here's one way, but it includes doing some MS stuff outside of
Java.
Word has its own object model which through Com or OLE, you can start up the WOrd application, open the document and the save as html, just as if you were doing it manually through MS Word. Then all you need to do is get that file and display it.
This might require a Java to Com bridge, which a company like JIntegra has such a product. .Net might also have a way to connect to Java too.
Now I thought that in most browsers, word documents can be displayed. Why would you want to change it to HTML?
Mark