Have you tried a reset? It rarely solves anything but sometimes does clear random error warnings. With no DVD loaded, turn the recorder on. When the "please wait" display goes away, hold down the left side STOP button (the one under the DVD tray) then while holding it down press the power button. The recorder should turn off, clear its memory and all settings will revert to factory default. You will need to set the clock and other things back to your preferences. While unlikely, this reset might solve your problem.
I've been repairing the 531-533-633 models since 2006, and I've never seen this "100H OVER" error display. The "100" is probably a numerical error reference, "H" could indicate "hours" or "hard drive"- either way, you're in trouble. The burner keeps track of how many laser hours have been used, its possible you've used the machine so heavily for playback or burning its gone past some sort of built-in odometer and signaled the motherboard for a replacement. Or, the machine may be indicating too many items on the hard drive or hard drive corruption. You could try to get into the setup menu and run the optimize HDD function as DebbyS suggests, but before doing that check how much breathing room you have left on the HDD- if its loaded to the gills with recordings, an optimize will just trash it completely. You should always have at least 6 hours of "available recording time" at the SP speed showing at the lower left corner of the HDD navigation screen- anything under 3 hours is risky and can lead to total hard drive failure. Sacrifice some recordings if necessary: delete them until you have at least 8 hours free space for the optimize function to work with.
If optimizing does not get rid of the DVD error, something else is wrong. It could be the burner is worn out, or it could be the operating system of the recorder has gotten corrupted. The 531-533-633 were very strange Pioneer models, unlike any before or since: they are easily corrupted, because too much of their operational software is tied in with the faulty TVGOS system on the hard drive. Once they start acting up, it is not practical to repair them: Pioneer service won't touch these models for any amount of money, and they are extremely resistant to do-it-yourself service. About the only thing you can attempt yourself is a burner replacement- if the "100H OVER" error is limited to something in the burner alone, removing it and putting in a new one may clear the problem. You would need to search eBay for a working Pioneer DVR109 or DVR-A09 generic PC burner, these sell for $20-40. When you get it, you'd need to remove the burner from the recorder, open both burners and swap their green controller boards, then put the new burner in the recorder (making sure to replace all cloth tapes, foil tapes, and foam pads in the same places).
The recorder should then work normally- if you still get an error display, the machine is irretrievably broken and your choice is to discard it or just use it as a hard drive timeshifting device. All three 2005 models are prone to irreversible breakdowns, but the the 533 and 633 often fare worse than the 531 which can sometimes be saved. Service is extremely difficult to impossible on these: other than trying a burner replacement, all service requires a special service remote and service disc ($100) + a Unix computer and special software, or a trip to a Pioneer Service Center that would be willing to look at it (most would refuse). Its more cost effective to replace a broken 533 with a new Pioneer Canada 460 or an American Magnavox H2160. Good luck!
