
This guide shows you how to transfer iTunes library from computer to computer with iTunes to iTunes Transfer
Step 1: Download and install iTunes to iTunes Transfer, first backup your itunes library.

Step 2: Select your preferred language, backup type and backup folder.
Step 3: Click the button on the skin and then, in the pop-up windows dialog, choose a backup name and typewrite the name of the creator (optional). Change the backup type if you want, then "OK".

It will automatically scan the iTunes library on your PC and start to backup. After backup, it's a folder in My Documents\iTunesBackup (if you did not change the default settings)
If you want to transfer the itunes library to your new computer, simply Copy the backuped folder to your new computer via your external hard drive,and then plug it in and copy to the hard drive of your new computer.
Make sure iTunes has been installed on the new computer, and just copy the contents of the iTunes backuped folder from your external hard drive to the new computer (in the same location as the old computer). iTunes will recognize the files the next time you run it. Done.