Preventing overwriting of sketch -- What is the best approach?

[in0]

@Arduino-x

I'd like to avoid the possibility that either I or some other person using the computer would inadvertently upload another sketch to the board...

I'm proof that it is possible. I have a Pro Micro permanently attached to my computer as a "macro keyboard" and I have accidentally uploaded sketches to it several times after selecting the wrong port from the Arduino IDE's Tools > Port menu while attempting to upload to another board.

Instructions for disabling the serial port in Windows are provided here:

Prevent Mega32u4 based Arduino resetting and/or uploading

Try this: Open Device Manager Expand Ports Double click on the serial port of your Micro Open the Driver tab Click Disable Click OK I recently did the same thing(except in an overly complex manner because I didn't realize you could do it this way) for the reasons you state and it has been nice not to have an extra serial port I never use cluttering up my Port menu in the IDE.

It's also possible to disable uploading on the Mega by putting a 10 uF capacitor between the GND and RESET pins, or by cutting the "RESET-EN" jumper on the board: