I've tried to update to the latest version of iTunes several times now and a little way into the process I get this message: "The feature you are trying to use is on a network resource that is unavailable. Click OK to try again, or enter an alternate path to a folder containing the installation package 'iTunes.msi' in the box below."
There are two paths shown and both return the message that iTunes.msi could not be found anywhere.
I'm not even entirely sure what's gone wrong here.
2. Use your favorite unzipping application (7zip or peazip are my tools of choice) to extract the contents of the itunes install exe, you should get several apps, one of which will be iTunes.msi.
3. When you try the update again, if it fails with the same message, point the updater at the newly extracted iTunes.msi.
"The file 'C:\......iTunes.msi' is not a valid installation package for the product iTunes. Try to find the installation package 'iTunes.msi' in a folder from which you can install iTunes."
But it's... it's right there!