I have replaced the power supply on one of my TivoHD that runs with an external drive twice now (within about 18 months). That particular TivoHD ran on a UPS for most of its life (except the last ~9 months). I have never had to replace a power supply on any other Tivo that I have own. Most of my other tivos to not run with UPS. I am fairly convinced that powering two hard drives is what caused the early failure of the power supply. Has anyone else experienced this?