Finding directions using a GPS unit is easy, however, not all file formats used by GPS companies are the same. Garmin and TomTom are two different companies competing in the navigation world. Both are capable of saving routes to the GPS unit, but they cannot use the same files. Using a third party file converter, you can change the format from the Garmin (.mps or .gdb) to the TomTom route format (.itn). As long as you have Java up-to-date, you should be able to quickly convert the file.
Download the Route Converter program from the download website and save it to your hard drive. It will be an executable file that runs when you double-click on it.
Download the Java program if your computer doesn’t have it installed. The Route Converter website will have a green check mark indicating if you have Java and can run the program. If not, follow the link to the Java download page and install the Java program.
Connect your Garmin device to your computer using the USB cable.
Double-click on the Route Converter program file that you downloaded in step 1. It will start up and search for files automatically on your computer, but you can guide it to your Garmin GPS unit by clicking on the file folder at the top right corner of the screen.
Select the Garmin route you wish to convert under the "File" option at the top of the File Converter program screen, then select “Route” under the option labeled “Type.”
Select the “Save As” type at the bottom of the screen. TomTom GPS units use .itn files. Click on the “Save” button at the bottom of the program screen once you have selected the correct file.
Disconnect your Garmin GPS from the computer by removing the USB cable connecting the two, and plug in your TomTom unit to the computer. Your TomTom GPS unit should have come with a cable that connects the TomTom to the computer USB port.
Put the newly created .itn file on your TomTom in the file directory located on your TomTom’s hard drive. You can access the TomTom hard drive directory by clicking the Windows "Start" button, then "Computer." Double-click on the drive labeled "TomTom" and then click the folder labeled "itn." This is where you should drag the saved .itn file to (the same one saved in step 6).