I'm confused about CNC software.

I always thought the CAM software is what sent the G-code to the hardware. But Visual Mill (a prominent CAM program) evidently only takes the 3D file (IGES, Rhino, Dxf, Dwg, STL, VRML, RAW, Point Cloud) and makes a tool path or G-code file. Then you need yet another program to send the G-code to the hardware. Is that correct? If so, which program is best to send the G-code to the router (Hardware driver like Rutex or Gecko)?
I've already got my Rutex drivers, and I really like Rhino-3d which I'm told works best with Visual Mill. So I've already gone down part of the path.

Rhiono-3d --> Visual Mill --> ??? --> Rutex

Another problem I have is I'd like to design on my Desktop (a nice machine) but use a rather old laptop to control the router (Compaq Armada - Pentium 200Mhz, 128Megs ram, SVGA, Win98). Any control software work with that?

Also, what do I call a program that sends the G-code to the driver, if it's not CAD or Cam?