First, if you have the App installed in your iPhone, please remove it.
Second, on your computer, go to Control panel and select, 'Folder Options'
Select, 'Do not show hidden files and folders'
and remove the 'Hide extensions for known file types'

Open iTunes and navigate to the applications folder. Locate your TomTom App. Back up this file before proceeding.
Right Click the App and select 'Show in Windows ...