You don't need a fancy computer with terabytes of ram and a superfast processor. You simply need a computer that will run the software needed to operate your CNC.
There are three types of software needed to operate a CNC. Design software (CAD) is used to create project designs. CAM (computer-aided machining) software is used to generate tool paths and convert them into gcode. CAM software also contains a feature called a postprocessor that edits the gcode to conform to the type required by the CNC controller. Finally, gcode sender software sends the gcode as a text file, line by line to the CNC controller.
Most CAD/CAM software is compatible with Windows. The computer you choose should be running Windows 7 or newer, with a minimum of 2 gig ram. The computer must have a monitor, a working USB port and a mouse or mouse pad.
Since the computer must be connected to the CNC while it is operating in a dusty environment steps must be taken to keep it clean.