Iphone 4 - retransfer data

[Kadach]

Hi.
After receiving my new iphone 4 mobile I transfered (by itunes) some data like (ebooks, music, wallpapers, etc) from my computer (dell not imac). Unfortunately, few days ago I had to reinstall my operating system on my computer, as a consequence I lost all previous files transferred to my mobile.
How I can transfer my files back from iphone to computer?
Chris