Have a read of this:
What’s a person to do when their hard drive crashes, and they lose all of the songs that they purchased from iTunes? There is no option to re-download all of your iTunes purchases offered through either iTunes or the Apple website. However, while you may get chastised for not backing up your iTunes library (which you will do from now on, right?), it is possible to redownload all of your iTunes songs purchased through iTunes again, and restore your iTunes purchases.
First, it’s important to understand that Apple has a policy of not letting people download iTunes music purchases more than once per purchase, and that undoubtedly has to do with royalties that they have to pay on each download. So you get to download the song that you purchase through iTunes exactly once.
And Apple strongly urges you (and rightly so) to backup your iTunes library (and of course you should always make a regular backup of all of your data).
But, shift happens, and what can you do if, somehow, you lose your only copies of the songs that you have downloaded through iTunes?
Well, as it happens, Apple isn’t heartless, and they do have a way for you to recover those songs that you purchased and downloaded through iTunes.
But first, you have to make absolutely sure that you don’t have any copies, anywhere.
Once you are really sure that those iTunes songs are gone, you can fill out a form at the Apple site, and explain your situation, and, as likely as not, they will very quickly flip a switch on your iTunes account, so that the next time you log into the iTunes store with the iTunes program, you’ll find that your iTunes selections are ready for you to download again.
Just don’t abuse it, and for goodness sakes, backup your hard drive!
Here’s the link:
Form to request to download iTunes purchases again