I've found sidlwidl to be a good program (get it from
www.sidlwidl.com). There is also one called Fiddle (get that one from
www.barbre44.com).
Sidlwidl is a .net application so you must download a fairly huge file (.net Framework) from Microsoft. Fiddle is a Java app.
Both show you what the graphics will look like in game.
I've found there to be a couple of problems with using sidlwidl: True/False tags are capitalized - EQ doesn't like this and ignores the flag altogether if it's capitalized. Wreaks havoc with text in windows. To fix, you must open the file in a text editor and find/replace such occurences.
I've not used Fiddle so I can't comment on how well it works. (Am downloading it as I type this actually).
The programmer of Fiddle has ceased development but has published the source. Sidlwidl seems to be in limbo.