Transferring from external to itunes

So my Macbook was stolen, but luckily I still had my Ipod with all my music on it! So my friend used iRip to to retrieve all my tunes and put it on an external hard drive for me. I just bought a Imac and I connected the the external hard drive and began to transfer all my music over, only a huge portion wouldn't transfer. All the songs were purchased on itunes and my old computer was deauthorized and the new authorized. It's random though. One song on an album will transfer, but none of the others will. Even though they were purchased at the same time. It says they're protected, but why do some transfer and some don't? Any help would be greatly appreciated.

If all the songs were legally purchased via iTunes, why not just re-download them again to your new computer? As long as you have already paid for them, you won't be charged a second time.

How do you re-download songs?

Set up iTunes with your existing account information

If chscag is suggesting that the iTunes Store will let you re-download songs you've purchased, I'm afraid he's mistaken. Apple occasionally allows people who've suffered catastrophic hd failure to a ONE-TIME-ONLY redownloading of songs they've purchased, but this is not the norm.

It's not Apple's fault; it's a restriction of the record companies. You can re-download APPS you've purchased all you want, but not music or video.

Can you not just connect your ipod, right click on it in itunes and transfer your purchases to the computer?

If this doesnt work then Sharepod enables you to take data on your device and transfer it to your machine:-

Sharepod for mac Free Download