Arduino and controlling a 3 axis CnC Milling machine

[Doddy]

**** NO EXPERIENCE HERE ****

(Agree with Adrian_S - the firmware running on the Arduino doesn't/shouldn't need reloading - that's a one-off configuration thing; re. drivers?, possibly - though that's just the serial driver which you may have already installed on your laptop).

I suspect what you have is an engraving machine with an Arduino running an instance of the open-source GRBL software. The Boxzy software would be the g-code streamer/manual control software to the Arduino.

If you're in a hole, I'd look at similar modern machines - they're all likely running similar g-code streamers and manual control software. You may need to reallocate I/O to match the pin mapping on your machine (or rewire) - that's can be "fun" for a while then it'd become tedious - if you're very lucky then many machines will have the same default mapping. But if you can't get the recent PC software to talk to the Arduino and you're really in a corner, there's very little to stop you flashing a new Arduino build for a recent machine, and using the up-to-date PC software. As above, the biggest challenge will be ensuring the I/O mapping is correct.