I've built GMP 4.1.4 for MingW and Pentium-4 with SSE2. And it and the demos, works great btw. Good job! If I distribute programs compiled with this library to users having only a plain old Pentium, will these programs run? Or just crash? IOW, does gmp have a runtime check that it really is running on a Pentium-4/SSE2 procesor? --gv