>One of the things I was worried about was that certain programs might see the .XLS extension and assume that it is an Excel spreadsheet, and therefore get confused. Maybe that's what's happening here?

Yeah. The problem is it isn't _really_ an Excel file, as we know. It's find if you can guarantee that only Excel will be used to open it, and if you can guarantee the user will chose an excel format when they first save it. But, frankly, some users will dislike getting a weird (to them) error about formatting.

I'm settling on, for now, just adding a DELIMITED WITH TAB option, which is simple, and then think on the best way to present it to the user so it makes sense. Silly little problem, isn't it? A COPY TO TYPE XL5 NOHEADER would be so nice. But I have no idea how that routine works. Might be difficult.