Most media files contain some form of tag which records details such as the title, track number, artist. etc. If you import such a file into iTunes then iTunes will read the tag data from it and list the data that it has found. For files which don't have a tag, typically those in .wav format but .mp3 files don't
have to have tags, the only information iTunes has when it imports will be the filename.
Although the tag can record much of the metadata (data
about data) of the file, certain information such as ratings, playcounts and playlist membership is stored in a database. There is a database for your local iTunes library and a database on the iPod. Putting the media files onto the iPod in their XXXX.<ext> format *is not enough* for them installed into the iPod's database. Despite your description above, if you were able to restore your iPod backup to a new device, then you must have backed up and then restored the whole drive, not just the Music folder. If you still have the whole image and a compatible device then you can do this again.
When iTunes places media on an iPod it uses the F00-FXX folders and XXXX.<ext> filenames in a scheme called a hash table. The details aren't important, but it is a way of efficiently relabelling files with much shorter filenames that won't clash with each other. As a by-product it also discourages casual piracy from the iPod's drive since you don't know which file is which.
If you only have the media files then, as you have seen, the best you can do is import them into iTunes. Those which have tags will be correctly reorganised. Those without will be given their current filenames as their track names and placed in the Unknown Artist\Unknown Album folder. I would suspect that most of these files will be in .wav format in which case you will have to listen to and rename them one at a time. If however there are files in .mp3 or .acc format then you may be able to build tags for them using
MusicBrainz Picard Tagger. iTunes won't detect any updates you make with third party tools, but I have a script for that called
UpdateTagInfo.
Given how easy it is for an iPod to be lost, stolen or damaged it should not be relied upon as the only place for your media. It makes much more sense to to maintain your library in iTunes on your computer, then sync that library to the device. Instead of backing up the device, which takes ages each time and limits you to replacing it with an identical device, back up the library.
*Fast backup for iTunes library (Windows Only)*
Grab
SyncToy 2.1, a free tool from MS. This can be used to copy your entire iTunes library (& other important data folders) onto another hard drive or network share. You can then use SyncToy periodically to synchronise or echo your library to the backup. A preview will show which files need to be updated giving you a chance to spot unexpected changes and during the run only the new or updated files will be copied saving lots of time. And if your media is all organised below the main iTunes folder then you should also be able to open the backup library on any system running the same version of iTunes.
tt2
