First thing to do is to find another SD card so you don't modify the original files, So the device can be put back as it was, but first have a look at the file structure, and note down what the path to the app is.
Should be something like...
*:\Route66\R66Navigate7.exeWhere * is the drive letter your PC allocatesThen go here...
How to install Tomtom 7 on dedicated PNA devices with Windows CE core 5And read everything, Download everything it tells you to.
To get Tomtom to start, rename the Navigator folder and Tomtom Navigator.exe to match the original card.
Follow the guide to activate the map, change the language and other settings
Post back if you get problems...