found this info- might help...
[ Copying iTunes Store purchases from your iPod or iPhone to a computer
* Last Modified: September 26, 2008
* Article: HT1848
* Old Article: 305465
Summary
If you purchased items from the iTunes Store and the only place you have them stored is on your iPod or iPhone, you can transfer them to any computer that is authorized for your iTunes Store account using iTunes 7 or later. This feature adds an extra layer of protection against losing your valued purchases.]
http://support.apple.com/kb/HT1848?viewlocale=en_US