Why not just download it and check the archive out for readmes or other info files? (Taking the proper precautions along the way, however.) I've never even seen the DirectX 5 patch work all that well on an NT4 box, though that may be more DirectX 5's fault than NT4's fault. I know people who would be very happy to be able to install a fully functional DirectX 6 or upward on their NT4 systems. If you find out what it is, I hope you'll post your findings.
Regards,
Jim