problems with download

What operating system and version are you using?

You've posted this in an OS X forum (and not an iTunes or Windows forum) which implies you're using OS X, and OS X includes iTunes.

The current version of iTunes is installed as part of the OS X  > Software Update... mechanism, so if you've used the update mechanism at all recently, you have the newest version of iTunes for your OS X release. Barring any software update errors or boot disk corruptions or other such, of course.

Given the Software Update approach for getting newer software is probably familiar, I might infer you're running an older version of OS X prior to 10.6 and are looking to get an iTunes update such as what can be beed for a more recent iOS device running iOS 6, and the way to do that is to acquire OS X 10.6 Snow Leopard from the Apple Store (it's around US$20) and install that, assuming your current Mac hardware supports Snow Leopard. Hardware requirements are available on that web page, and you can view your current hardware details via  > About This Mac (possibly including the More Info button) mechanism.

In general and FWIW, you can't and shouldn't install a newer version of iTunes onto an OS X version older than it's intended for. That won't work, and might well cause problems or corruptions if the installation is "forced" to load iTunes.

If I've guessed wrong here (which is entirely possible), please consider posting a few more details around your current hardware and software configuration, and why you're trying to manually update iTunes.