I bought a Hitachi Deskstar HDP725050GLA360 500G SATA hard drive to upgrade the 160G stock hard drive in my TiVo HD, and it will not work in this application. Win_MFS copies the partitions just fine, and I can read and write all the ordinary files using a Linux boot, but no matter what, the drive will not boot. Instead, it enters into an infinite reboot loop before even loading the OS. I went down to Wal-Mart and got a Western Digital 320G, and it boots just fine. It seems evident this model is incompatible with the TiVo Hd, at least as a primary drive. Why, I don't know.