How to reinstall iTunes 4.7.1?

I recently upgraded to a version 6 on iTunes but once installed my iPod would not be recognized by my mac. I've deleted iTunes 6 and installed version 5 but this wold not read the iPod either. I've now deleted 5 and tried installing version 4.7.1. However, once I get to installation type iTunes package is disabled and I'm unable to install. Can anyone please help as I now am left with no iTunes installed and unable to install the version I want.