I don't know of such a program. There are ways of doing it that are slightly more labor-intensive, though--the Word search function is pretty powerful, so you can search for things in italics, and then put <em>^&</em> in the replace box. (The ^& means "thing you found.") (I should say, test this before you do the whole document, I don't have Word and can't...)

brief tutorial and in-depth description of all possibilities.

(I feel like this should be possible to do as a macro and distribute it, but I don't know how...also, see above re: no access to Word.)