From the producer:
Upgrade your Metroguide to a "Gold" product with MetroGold! With
MetroGold you take your MetroGuide to the next level using all the
functionality it can offer.
In Garmin MetroGuide, North America and Europe version, automatic route
calculation is offered in the PC only. There is no route calculation
data that can be transferred to a GPS even if it has autorouting
capabilities. With MetroGold you can make your GPS capable of
autorouting with MetroGuide maps. MetroGold will upgrade your
MetroGuide to have this functionality. You can upload up to 4Gb of maps
to your GPS.