was originally going to install windows XP on a raspberry pi environment, until I found arduino.
The Arduino is a sensible choice for interacting with the hardware. I'm not sure whether you would be using ordinary DC motors, or stepper motors, or servos. Servos would be very convenient in many ways because the contain their own drive circuits, but you would need to go into your requirements for the 360 degree motion in more detail to know whether a servo was a sensible choice for that.For driving DC motors or a solenoid you would need a driver circuit. It's possible to get Arduino shields which plug onto a standard Arduino shaped board to drive two motors or motor + solenoid but you would need to check the electrical specs to see whether these were up to the job of driving your devices. It's also possible to get Arduino clones with the motor drive circuits integrated onto the main board and if you only need a small current (say under 1A) that might offer a smaller and cheaper solution. You can also get more general drivers which need to be mounted separately and would be wired to the Arduino. You would probably need something like this for larger motors or if you wanted to drive more than two motors.In order to provide remote access to the control interface you *could* use RDB into a windows desktop but a cleaner solution would be to create a web app on the PC which uses the serial connection to send commands to the Arduino and get status info back from it, so that you can access the UI remotely from any web browser without needing the hassle and security vulnerabilities of desktop access. This would make it possible to access the UI from smart phones, tablets etc and not just devices with RDP client support.