I have an iPod Classic 6th. gen. of 160 GB. I manually manage the songs, so I do not have any backup on my computer (nor the “itunesDB.old_mlpmp” file in the “iPod_Control/iTunes” folder in the iPod’s HD).

The problem I had was that one day I unplugged the device from my PC and suddendly no songs were shown on the iPod, even though the files were still on the HD and the same space as before was displayed as “used”. I plugged the device to my computer and a message similar to

“iTunes cannot read the contents of the iPod ”xxx’s iPod”.
Go to the Summary tab in iPod preferences and click Restore
to restore this iPod to the factory settings.”

showed up in iTunes. I checked, and the mp3 files actually were in the “iPod_Control/iTunes” folder.

The first this happened to me I took all these archives, moved them to my PC, restored the iPod, and moved the files back to the device using MediaMonkey. Since at the second time I did not want to repeat that process which took me A LOT of hours, I started to look for ways to repair the iPod’s database file (iTunesDB).

First of all, I want to make clear that this is a solution that worked for ME. I cannot guarantee any results and cannot provide support in case of failures. Please use this method at your own risk. I am posting this for the reason written at the start above.

OK, here’s the solution that “enabled” all the songs back into my iPod:

-> Download MediaMonkey from its author site and install it.

->Connect your iPod to your computer (mine was Windows XP, I think this doesn’t really matter).

->*Make sure once the device was recognised by the program it doesn’t say “Searching…” (or similar) on the entry of the device on the left pane of the window.* Erasing the folder “X:\iPod_Control\iTunes” might help with this (it is recreated automatically; back it up to your local HD though).

-> Right click on the device’s entry (e.g., “John’s iPod (L:)”) and choose “Rebuild device’s database” (or similar). *I am not fully sure this feature is included in the free version. Sorry about this.* Wait until the process finishes. For me, having +- 18000 songs (+- 120 GBs), this took no more than two hours.

-> Unplug the device safely. The iPod will still say “o Songs” at the main view, but if you go to Artists all of them will be there.

->Now plug the device again to your computer and open iTunes; this will take care of the problem described in the previous step.

->Unplug it again safely and you should now have a full recognition of all the songs in the device. Of course, all playslists will be gone, some songs (like former voice notes) will have faulty tags/names  and many more (in my case +- 13000 songs) will be shown as compilations, what means all of these won’t show up in “Artists”, but in “Compilations”. The latter can be easily fixed, by using the smart playlists iTunes’ feature (make it show only compilations, and then do a massive  edit to the playlist by putting “No” in the Options tab -> Compilations field).

Hope this has helped you. I will appreciate any comments and criticisms.