I had Mach3 installed on a touch screen computer using a via chipset and CPU, running Windows 2000, and it worked great other than being slow. I bought a Pentium 4 based touch screen computer, installed a fresh Windows XP, Mach3, copied over the config, and hooked it up to my existing CNC. It seemed like the parallel port was completely dead. No heartbeat to turn on my G540, no limit switches detected, nothing. I uninstalled and reinstalled Mach3, and tried to set it up manually. I thought maybe the new port couldn't supply enough voltage or current to the G540, so I got a C26 buffer board from cnc4pc.com. Nothing. On the BIOS, it was set as EPP, but I try ECP and Bi-Directional as well, with the same results. I disabled the parallel port on the Motherboard, and installed a Moschip MCS9865 based PCI Parallel card. Same result (Although there weren't any port address settings in the driver, I selected LPT1, LPT2, and LPT3.) I suspect nobody will know exactly what's wrong in my particular situation (I still welcome advice!), but I'm hoping someone could suggest some tools for troubleshooting the parallel port. My bag of tricks is empty.