For some reason, your computer copy of your music has gone (e.g. hard drive failure, accidental delete, reformat or now belongs to someone you don’t get on with any more) but your iPod is full of music. Panic not.
If you have an iPhone, use Sharepod if you are on Windows. Use DeTune if you have a Mac. These will both allow you to copy the music from your iPhone to a folder on your computer. You can then Add Folder to Library as normal in iTunes.
Get the music off the iPod onto a computer
1) First thing is to try on your computer (or a computer you have access to with iTunes on it):
Follow the instructions from here with some comments from me. If any of the messages / warnings seem unclear or scary, stop.
If you see this one, say NO!
How to transfer music to an iPod to a Windows computer (assuming the iPod used to be synced to a Windows PC, not a Mac)
Step 1: Connect your iPod and launch iTunes. In the iPod management screen (click on “<your-name>’s iPod”or whatever in the Devices list on the left), scroll down to Options in the middle centre and check “Enable disk use.” iTunes will give you a warning. Check it says something about requiring manual ejection even when automatically syncing. If so, select OK.
Note: If you get an error message asking you to reformat upon connecting, STOP!. Your iPod was originally formatted for Mac and cannot be used in Windows. One workaround is to install a program like MacDrive, which will allow your Windows machine to read Mac-formatted drives. Clicking “reformat” will erase your iPod.
Step 2: Now open My Computer and open your iPod folder which you should see along with C: and any other drives on your machine (CDs, DVDs and the like).
Step 3: Open Tools > Folder Options. Click the View tab and check “Show hidden files and folders” which could be a radio button in the middle somewhere. (If you can’t see the Tools menu, press Alt once and it should appear)
Step 4: Now in your iPod folder, open iPod_Controls folder. Highlight the Music folder and drag it into the desired folder on your PC (I’d suggest dragging it to the desktop). This might take a while, depending on how much music you’re transferring. Once this is done, your iPod is backed up on your computer. We should be able to get it back if anything goes wrong later.
Step 5: Highlight all of the folders again, right-click, and select Properties. Uncheck “Hidden.” Close this window.
Once the files are copied, you’ve successfully transferred the music from the iPod to your computer. However, you’ll notice that the songs have four-letter names and are scattered among many folders. It’s OK. Once you import the music into iTunes (or any other media player), the program will reinstate the titles of the songs.
Check other backups
If you have access to any kind of backup of your information, the Music folder is normally at \Documents and Settings\username\My Documents\My Music\ or \Users\username\My Music\ (where username is probably the only one that is in the folder, not Public or Default). Copy these onto your new computer (e.g. using a USB drive).
Add the music to your new iTunes
Fire up iTunes on your new computer and choose File>Add Folder to Library… and navigate to the files you copied above. This could take a while, but should leave you with a fully populated iTunes library which you can then sync with your iPod.