By default it is impossible to extract songs from your iPod to transfer them to another newer or older iPod. But there is a way around this. When you add a song through iTunes it stores the song in a hidden folder in your iPod. You can access this folder through one of these methods:
1. Open My Computer.
2. Click on Tools.
3. Click on Folder Options.
4. Click on the View tab.
5. Scroll down until you see the option for “Show hidden files and folder”
6. Click on the circle next to that making sure it is filled in.
7. Click OK.
Then open the drive that represents your iPod and you will see the folder called iPod_Control. Open it
Method 2 (For Windows XP only)
Open the drive of your iPod in My Computer. On the address bar it may say for example iPod F:\. Type in front of it iPod_Control and press enter. The folder will open.
Now you can extract songs from the iPod. Open the folder named Music. There will be several folders with weird names containing songs. Copy these folders to your hard disk. You can now add these songs to your other iPod through iTunes. If all your songs are in MP3 format then you can search the main folder with .mp3 and get all the songs in one place. You can do the same for AAC music files and if you have both types mixed then you can search both file types separately for getting all the files to add to your iPod.