The reason why it doesn't work is because your iTunes on your laptop finds the files differently than your desktop. Sadly, its not automatic.
What you have to do is get all of your music files onto your external, move them all to one central file (i.e. "My Music") then install iTunes regularly onto your computer.
Then in iTunes you go to: Edit > Preferences > Advanced tab >
And in the "iTunes Music folder location", you select the "My Music" folder for example, where all of your files were just moved. Then in the same window under the Advanced tab, check the box that says "Keep my iTunes folder organized."
Once you click "OK", iTunes should start to organize your music files.
Edited by Matt B, 24 December 2007 - 02:38 AM.