I bought a Western Digital 1TB My Book AV DVR Expander, powered down my THR-22, connected the drive, powered up the drive, waited a little bit, powered up the receiver and the receiver did not recognize the drive at all. How I got it to work: Hook the WD Drive up to a Mac using USB. Launch Disk Utility and select the WD HD on the left. Don't select a partition (indented). Select the actual disk itself. Under the Partition Layout drop-down menu, select 1 Partition. Below the box where it lists "UNTITLED 1" click the Options button. Select GUID Partition Table and click OK. In the Partition Information section, leave the Name alone but change the Format drop-down menu to Mac OS Extended (Journaled). Click Apply and wait for Disk Utility to do it's little dance. Once it's done, close Disk Utility then drag the drive from the desktop to the trash/eject icon and disconnect it from the Mac. Power down the receiver, connect the (powered down) hard drive to the receiver using eSata (of course), power up the hard drive. This unit had a power button on the back that I had to press to power up the drive. Just make sure the drive's power light is on BEFORE powering up the receiver, otherwise the receiver won't recognize the drive. Once you've had the drive powered up for 15-30 seconds or so and it's nice and spun up, power up the receiver and you should (fairly shortly) see a message that the drive is being formatted. Once that process is complete, you have to repeat guided setup because external drives on the THR-22 work the same as the DirecTV HR series, that is it's either the internal drive OR the external drive. They do not, sadly, work in concert to make a big ole happy drive. Good luck and happy recording!