I intend to intall mach3 on Windows 10 OS. Will I need to install the USB Motion Driver RnRMotion.dll? I attempted to download this but it was blocked by Windows 10.

Yes, Mach3 (the software profram) will work with Windows 7, and windows 10 when coupled with the Mach3 USB interface. If you intend to use the parallel port driver, stick with Windows 7 in 32-bit mode. Additional Information: Rnrmotion.dll is a dynamic link library which is very similar in function to an executable program, or app. Since a dll is executable, malicious code can be embedded in that type of file, so windows will automatically flag all files of this type. You just need to make sure you are downloading from a trusted source. The emotion.dll file on our site is clean, but still run run windows defender against it to make sure. Additional Information: