I followed the "XP Optimization" instructions in the "Downloads/Mach and Lazycam/Win XP Optimization", above. I had been running Mach 3 for over a year without any problems, then last week started getting the "Driver Watchdog Triggered" error after about 3-5 minutes of running a project. It's an old but good computer so I didn't think something had gone wrong with it. Things would run well for a while after I had restarted the computer but the watchdog error was persistent. I cleaned up the computer using the instructions and ran Mach 3 for over three hours (cut air with several projects) and it's working like it used to. Cleaning up the Startup Registry, wallpaper, disk, etc, also fixed an intermittent glitch in the Auto Tool Zero I had. Every once in a while, the machine would "hiccup" and set Zero before the tool actually touched the tool height platform on my digital probe. It's well worth running the checklist!!!!!!!!!!!!!!!!!