Itunes 9 Help

Hello,

Hi I've been trying to install the new itunes 9. for about a week now and i keep getting the message " the feature you are trying to use in on a network resource that is unavailable
click ok to try again or enter an alternate path to a folder containing the installation package "i itunes.msi in the box below

I have also carried out all the steps on the apple website

https://support.apple.com/en-us/HT204275

Any Help would be brilliant thanks
Louise