I have owned and serviced more Pioneers than I can remember, every model except the goofy DVD/TiVO units. I've had the OP's problem come up a handful of times with all vintages, with both EIDE and SATA HDDs. As others have suggested, the problem is not limited to Pioneers but all DVD/HDD units, and to some degree user error is involved: letting the thing fill to 100% is a major no-no because results are unpredictable. I have mentioned before from time to time, and others have hinted in this thread, but it bears repeating with emphasis:
DVD/HDD recorders are dumbed-down single-purpose dedicated "workstations" intended for casual timeshifting and making basic edits before burning DVDs. While they do contain processors, hard drives and optical drives similar to a PC, they are not PCs
: they do not have advanced PC operating systems with built-in automatic correction of HDD errors
, and you cannot use a "utility" to repair them. Instead, they rely on the minimal ability of modern HDDs to police themselves, and they rely on users to heed the warning screens the machines display saying "make room on the HDD right this minute or you risk dire consequences."
If you do
ignore the warnings, accidentally or on purpose, the recorder will not stop you from running out every last bit of headroom on the HDD. At that point, you play the odds: sometimes the HDD can be brought back from the brink by deleting a certain amount of material, other times the HDD becomes "locked" in 0% capacity mode until you invoke a full erase/reformat or bring the unit in for service. Statistics indicate your luck somewhat depends on age of the HDD, how often you add and erase recordings, and how many edits you've made on the HDD: a recorder filled with blocks of complete unedited TV shows and movies is more likely to "wake up" when a few titles are deleted than a recorder whose HDD is completely filled with TV shows that have had the commercials cut out (or has lots of little clips like music videos). Also note a certain small percentage of HDDs are inherently faulty: they pass initial inspection at the factory but are ticking time bombs that self-destruct a couple years later: they just get stuck, and can't be un-stuck.
Most recorders have some kind of provision for emergency erasure/reformat of the HDD, although it might involve removing it from the recorder and erasing in a PC before the recorder will agree to format it. Pioneers (and Sonys based on them like the RDR-HX780) also have an extremely inconvenient requirement you use a special Service Remote and Service DVD for some HDD repair/replace tasks. If your HDD is "stuck" but still allows playback, you could play the videos out to another recorder and save them that way before reformatting the HDD. If it allows burning DVDs, you could get the recordings off the HDD by making normal DVDs, even if editing is disbled. If the recorder is a Pioneer model from 2005 or later (530/630, 540/640, x50 or x60), you have a little-known backdoor available (as long as the machine still permits burning DVDs from the frozen HDD): VR-mode backup/restore DVDs.
"VR" is a term used in confusing ways by various recorder mfrs, but with Pioneers it refers specifically to an optional proprietary format you can apply to blank DVD-R, DVD+R or DVD-RW discs. Load a fresh disc, go into the Home Menu>Disc Setup screen, and select the "Format As VR" option. In less than a minute the machine will mark the disc as proprietary. From that point on, any recordings you high-speed dub from HDD to that DVD will be preserved on the DVD exactly as they were on the HDD and can be reverse high speed copied back to the HDD with no loss of quality and all chapters, thumbnails and edits intact. While this can be time consuming and tedious to do, it at least offers a restore opportunity: format a stack of blank DVDs to VR Mode, copy everything off the HDD in high speed mode, erase the HDD to repair it, then restore all the recordings back to the HDD by reverse HS copy from the VR DVDs. You don't need to back up the entire HDD unless you want to: just back up anything you'd rather not lose. Then, delete everything
on the HDD and see if you get a proper capacity readout: if so, you can then restore the important recordings from the VR discs. If not, you'll have to erase and reformat the HDD (or perhaps replace the HDD with a new one).
Note the VR Mode backup dvds can only be played on a Pioneer recorder, they are not standard video DVDs but "file" dvds. (I believe you can use DVD+RW media for Pioneer HDD backup as well, without needing to pre-format as VR, but have not personally tried it.) If your Pioneer model supports DVD-RAM, you can also use RAM discs to copy files off the HDD and restore them later. RAM discs do not need any special VR formatting, they can be used as-is. The drawback of DVD-RAM is dead slow dubbing speeds and the higher cost of RAM media (a 160GB Pioneer 640 HDD would need about 40 discs to completely back up). Other than making backup/restore DVDs, there is no practical
way to extract, copy or salvage the videos from a Pioneer HDD. By practical, I mean for a normal user who is not interested in spending a month or two tinkering. If you're a computer geek who understands things like Hex Editors, it is possible
to put your jammed Pioneer HDD into a PC and pry the videos off in little chunks, slowly re-assembling them as MPEG2 files. I would rather have my toenails pulled out with pliers, but if you groove on that sort of endless flying-blind computer work see AVS threads such as this
for additional info. Most of the threads reference Panasonic and Funai recorders but the same principal applies to Pioneers.