You need to buy the operating system upgrade to OS X 10.6,which requires 1GB of memory. Call the online Apple store, which in the US is at 800-MY-APPLE, or order OS X 10.6 online at http://store.apple.com/us/product/MC573/mac-os-x-106-snow-leopard . Install it, do Software Updates until no more are available, which will get you to OS X 10.6.8, at which point you can install the latest iTunes.
Thanks Apple, for screwing a loyal customer, who has spent thousands of dollars on your products for years, into not only spending a little bit more money, but into having to carry a phone with zero information and apps while also carrying an old phone with no communication, but containing vital info and apps until his disc shows up to enable transfer of that info. I'm sure its pretty hard to make that software available for download.