No DOS programs whatsoever work in XP for me. Jazz 1 runs fine in DOSBox, though.

Back on the subject of floating point: OpenJazz uses the number of seconds per frame for its calculations. However, an integer is used for the number of milliseconds per frame. All I need to do is make calculations on the basis of milliseconds rather than seconds. In fixed-point arithmetic, this could be done with an exponent of -10. 2^-10 is very nearly the number of milliseconds in a second. I'll give it a go.