Tomtom one map of Greece

The usual way to update your TomTom GPS is using the TomTom HOME software that you download and installed on your computer/laptop. Then set up your TomTom account (using the TomTom HOME application) and registered your TomTom device (in that account) on the TomTom webiste
After that, connect your TomTom device to your computer/laptop (using the USB cable). Turn on the TomTom device, and touch the YES icon (on your TomTom screen) if it asks whether you'd like to connect to the computer.
You should be able to see the updates available for your TomTom device (on the TomTom HOME application). Select the updates you want and (download and) install them.
Recently TomTom has stopped providing software/map updates and/or support for certain (older) models of their TomTom GPS. If you see such a notice when you register your TomTom device, your option is to get a newer GPS model (you may even get an offer on the TomTom HOME screen), or you can continue to use your device without updating the software and/or maps until it becomes unhelpful, unreliable, etc.

You were able to successfully download windows files with your Mac and transfer them to your Tom Tom? I'd suggest trying the transaction again, but doing it with a windows machine. (Trust me, I have a Mac and I realize how unwell it likes to play with Windows.) {But I wouldn't trade it}

Reinstall TomTom Home and you should be able to update the maps. TomTom's customer support is also very helpful and can troubleshoot you through the issue- http://us.support.tomtom.com/cgi-bin/tomtom_us.cfg/php/enduser/std_alp.php

You can download the map from TomTom here

Unfortunately there is only a limited amount of space on the ONE. You can back up your Tele Atlas maps on a laptop using TomTom Home. As long as you have your maps backed up in TomTom Home, you'll be able to install each set of maps on the fly. It may seem like a hassle, but it's better than having only one set of maps

Do you have Bit torrent/ Ares or other torrent downloaders?
If so download torrent and open with bittorrent or Ares

Two options for upgrading:
1.) You can either purchase the hard copy on an SD card here at Tele Atlas- http://www.teleatlas.com/ForConsumers/MapUpdates/index.htm

2.) Another option is upgrading directly from TomTom at their Map Store- http://www.tomtom.com/products/maps/select.php

You could probably just manually delete the Canada/USA maps from the device, and copy over the europe (or whichever ones you need) to the device. 
Just plug it in, and view the memory like a normal usb drive..delete the old, copy over the new.
Don't forget to use tomtom home to backup your gps device to your computer first (thus saving your canada maps for later..)
Afterwards, you would probably have to go into your preferences and choose the europe maps.
Good luck!

This TomTom comes loaded with 2 maps....Guam and the US with Canada. I too got stuck in Guam and it is not obvious how to get out of it. But here it is.
Go to Main Menu, then Change Preferences
Hit forward arrow twice
Go to Manage Maps
Hit forward arrow once and choose Switch Map
It should show you Guam and the US and Canada
Tap US and Canada and it should take you out of Guam!!
Mine did and I am now going to delete the Guam map.

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