I want to open Narrator from another program and have a .mtx file pre-loaded. Is this possible with Narrator?

Colleen,
narrator is written as a hta application and at this point does not support command line. But it should be very easy to extend to accommodate this functionality. There is a very nice description of HTA(s) and parameter passing at: http://msdn.microsoft.com/library/default.asp?url=/workshop/author/hta/reference/objects/hta.asp

Also we are going to put your request on our list of things to do for the next release of Narrator, but in the mean time, consider the suggestion above (and if you succeed, please let us know, we could publish your enhancements on our website

-- ales