1) depending on what you want to do, you may be able to use a 2D CAD program.
2) Mach3 is a machine control program. It does come with a free, basic CAM program (LazyCAM) that works with 2D drawings only.
For 3D models, you need a 3D CAM program. There are at least 2 that work inside Rhino. RhinoCAM and MadCAM.
3) Assuming you're talking about about a machine control program?
Mach3 will run on a 64 bit system, but you can't use the parallel port. When using Mach3 on a 64 bit system, you need to use an external motion controller, such as the Smoothstepper. Warp9 Tech. Design - Home of the SmoothStepper - Home