To add a reset switch to the SX, you need to install a momentary contact pushbutton (normally open contacts) across capacitor C45 (a 0.1uF) on the CPU board. That small capacitor is connected to pin 2 of VG7, a 555 timer IC wired as a "one-shot" circuit. The other component on that pin is a 1 Megohm resistor R23. The added switch goes between pin 2 of the IC and ground (across the capacitor). Momentarily grounding that line with the added switch triggers the one-shot. The circuit holds long enough that all devices are properly reset. It's what happens when the computer is powered up. That is the preferred way to do it, although grounding the output side of that chip through one of the ports will also work, if you can accept the risks involved. As I said in the article, I suggest you install a 100 ohm resistor in one leg of the line to the switch, just in case you get the connections wrong... it will do no harm, it just will not work. I'm at work right now, so I can't peek inside my SX to locate the best mounting place for a switch. I did install a drive select switch to my SX. It's a slide switch, flush mounted inside the left side panel so it barely sticks out with little chance to get accidentally bumped or broken.