I've searched the upgrade FAQ and don't see any mention of whether the TiVo HD models use SATA I or SATA II drives. Looking at the original WD drive from my THD, it has a jumper block but the label mentions only adding a jumper to Power Up In Standby. Most SATA II drives include instructions for adding a jumper to limit the drive to SATA I speeds, where the application requires it. So far then, the original WD1600AVVS looks like a SATA I device. So... Looking at WD's description of the WD1600AVVS I see that WD says only that it requires a SATA connection. Clicking the WD Interface Guide link, takes you to a page that says that SATA drives have a 150 or 300 Mbps data rate. No help there as they don't distinguish SATA I from II. Of course, even if the WD1600AVVS is a SATA I device, that does not necessarily mean that THD cannot handle SATA II drives; its controller may in fact be SATA II. The bottom line is this: should an upgrade SATA II drive put into a THD have the jumper installed limiting it to SATA I speeds? It would be handy if the FAQ mentioned this.