I am by no means an expert on this subject, but after poking around for 10+ hours on the various forums I found a lot of "mis"information concerning external SATA hard drives and replacing internal hard drives in a Direct TV DVR. I am not going to go into great detail but instead focus on the route I choose. This is what I learned: The THR22 is the same as the HR22, the only difference is the operating system. The good news is the operating system no longer lives on the internal hard drive like the older DTV/Tivo units. All one needs to do is replace the hard drive and reboot. (Preferably with a video rated hard drive, such as I did with a 2TB Western Digital WD20EURS.) The bad news is due to the flood in Thailand last year, the supply of these drives have "dried up" worldwide. Maybe someone can offer suggestions for alternatives to the the Western Digital Video rated drives? There are 2 ways to go about adding hard drive space to you THR-22. (In both cases you loose all shows and programming on the original internal hard drive.) 1.) Add an external Drive with SATA connection (Lots of recipes for failure depending on the brand/model of Hard Drive and External Case you use) 2.) Open the case and replace the internal hard drive. (Simple and straight forward but you void the warranty and some by-laws) I decided that finding the correct external SATA drive/case option was to much trouble, even DTV does not officially support them. So I went the internal route, here are the 5 easy steps if you are computer-savy. 1.) If you are afraid of the warranty issue. (Stop right here) 2.) Unplug the THR22 and disconnect all cabling. (If you can't re-connect the cables .. Stop right here!) 3.) Open up the case. (If you can't do this then stop right here) 4.) Replace the hard drive. (If you can't do this then stop right here) 5.) Re-connect all the cables and plug it in. (The THR-22 will automatically format the drive upon power up.) I have been enjoying my new 300 hour HD recording capability on my THR-22 for over 2 weeks now. No issues! Choose wisely my friends!