I recently reformatted my hard drive and lost all of my music. Is there any way I can reinstall iTunes and add more music to my ipod without having to erase everything already on there?

This is pearl jam related because 90% of my music on there is PJ.

If you want to transfer music from your iPod back to your hard drive, there are plenty of 3rd party work-around programs available. Check out the downloads section at http://www.iPodLounge.com