Last year, my hard drive went bang and I lost all my iTunes purchases. Apple said that i would have to rebuy everything i lost.
Now they have given you the ability to redownload everything for free (although you paid for it in the first place.

Upgrade to the latest version of iTunes, click on "Purchased" under the "Store" tab, then down in the bottom right hand corner, click "Download Previous Purchases".

Im in the process of re downloading 1468 songs from my old account zzzzzzzzz