I recently purchased one of the recommended Western Digital 1TB SATA hard drives to extend our DVR capacity. When trying to install it, the DVR wouldn't recognize the drive. I worked through diagnostic steps with the Verizon Tech. Ultimately, they decided to send another DVR assuming my current unit was defective. When the new DVR arrived, we had the same problem. After spending more than an hour with a Tech on the phone again trying to get the DVR to recognize the drive, she said I'd need to contact Western Digital for support. I went to their website and found a very simple step in the process had been overlooked, and the Verizon Tech's appear not to be aware of it.
When you install an external drive, you start the steps through the DVR menu options to add storage. Have the new external drive plugged in to the AC power but DO NOT plug the eSATA cable into the back of the DVR until you are promoted on the TV screen through the setup menu to add the drive. If the eSATA cable is plugged in before you are prompted for that step on the TV screen, the DVR will not recognize the drive. It will let you go through the rest of the installation set-up and will reboot the DVR, but the external drive isn't recognized.