I recently endured another TiVo failure, though this time it was much more of a drawn-out process rather than a single catastrophic event. The most common problem with DVRs is hard drive failure, since the drive is working pretty much all the time, even if you are watching live TV and not recording anything else, and even, to an extent, when the DVR is "turned off."
So the drive failed, but in this instance I knew it was coming for months, because we were having random problems with recordings. The image would freeze, and then sometimes pixelate as the DVR tried to move past the problem spot. At first these were minor issues, and in some cases we could escape from them by fast-forwarding a little.
But as the weeks went by the instances got more frequent and more serious, to the point where the TiVo would have to restart itself, a process which takes at least five minutes. Also, if a show we were watching got "stuck" while we were recording another show, the recording in progress would also be ruined. Eventually we could not even watch live TV for more than 10 minutes or so before the bad hard drive caused shows to stutter and then freeze, leading to an eventual reboot. We even had to unplug it in order to keep it from continuously trying to reboot itself. Needless to say, the unwatched recordings on the drive were lost to us.
When the hard drive fails, there are two options: get a new unit, or replace the drive in the existing unit. Tomorrow I will explore those in more detail.