I have a Series 3 model, which was the first to support external drives, and did so before there even was a Tivo-branded drive. So I went to the Tivo forums and bought the most popular drive people were using (a 750GB Seagate) and the most popular enclosure (a very nice Antec model with great, quiet cooling.

This solution has worked flawlessly for about two years, aside from the annoyance that when the TV was off and it was silent in the room, it was quite easy to hear the hard disk, even when nothing was recording.

But then there's last month. Our Tivo started freezing quite a bit and rebooting. I posted this and several other symptoms to the Tivo forums, and they correctly diagnosed it as hard disk failure on the external drive. I removed the drive, which wipes out all of the recordings, and everything is fine now, aside from having an annoyingly small amount of HD recording space (I have to be super vigilant or we lose a lot of recordings).

Eventually I plan on getting a new external drive, but I think I'll go with the Tivo-branded one this time, despite the higher cost. I know that Western Digital's MyBooks are seriously quiet (I have two on my desk right now and they're silent), and I think these would be more suited to the task of being used on a DVR.

So my suggestion is to replace the drive (not easy) or get the Tivo external drive (easy, but not entirely inexpensive).