You'll either have to upgrade the OS on your computer or get a newer computer if that's not possible. The new iPhone 6s will be on iOS 9 and will require the latest version of iTunes, which, unfortunately, you can't get on your existing computer.I am working on a windows xp computer and ITunes 12.1.2 Will the IPhone 6s work on this set up?
Will I be able to transfer all my stuff that is on my IPad 3 and my computer to this phone?
As has been said above Windows XP won't work with the latest version of iTunes, Furthermore Microsoft doesn't support XP anymore so theres no help to be had there.Install the latest iTunes, it will work on your XP Windows PC.