Keri,I think I don't understand. Here are a XyWrite 4 file and an RTF ANSI export:
http://www.columbia.edu/~em36/MoreXy.zipI created these using Carl's setup, very slightly adapted. The RTF file has two characters replaced by underscores. If I understand your message correctly, this shouldn't happen - unless there's something else I need to do in order to set the code page to 437.