Let's clarify:
Are you 100% positive the driver won't install, or 100% positive that the computer won't recognize the MyDMX hardware?
You also failed to mention how you're connecting, and have you tried another USB port?
Anyhow, MyDMX support files are sitting on my server:
http://www.studio42.com/mydmx/
I should have the directory wide open. Enjoy.