Montana 610T. Only 3.54Gb available? Selectively remove maps?

Yes, free space looks correct.

Not sure what you mean by which file you copy? BaseCamp will install any maps available to the card if you select the card and right click and choose Install maps.

Maps will always be available in BaseCamp, so will BirdsEye but once that subscription expires you will no longer be able to send them to your device. It's recommended that you copy BirdsEye files to your hard drive, as from there you can always copy them to your device after the subscription period ends.

I read you had to copy the GPS device ID file to the card before installing maps to the card. I'm guessing so the server can see the card as a Garmin device and install the BE files. After that, all I have to do is insert the card into the GPS to view the images right? Unsure how extreme the Garmin DRM is(before/after subscription expiration).
Also, can I delete unused geocaching or individual topo files of areas I don't need?

Not if you're using BaseCamp to install the maps? It would perhaps help if you explained exactly what you're trying to do?

As for deleting areas you don't need this depends on the map.

I got it worked out. I placed the GarminDevice XML file onto the 32Gb memory card so it sees it as a Garmin device so it can download to it. No need to have the GPS plugged in. Also deleted some French and Spanish voice files for a little bit more space. Geocaches are too small to bother. The world basemap is just one big file.
Now I can download everything I think I might need for a year and save it elsewhere to be used whenever I want. :)

.....
Can I delete anything to create more space on the 610T? ....?

Ok before anyone starts to delete any files on there units... make sure you got a working backup copied to your PC-HD some where !!

that way you always got a backup in case some thing go's wrong, or you want to be able to restore the Montana to it's factory state to be able to sell it on to a friend in case you fancy a newer model or just another one in future, so do your self a favour and make a backup just in case... ;-)

Anyway... from the day I had the unit, I started to make some space and deleted quite a lot of files and folder which where no use to me... made room for about 360MB ...

here a list of folders and files which can be deleted with no harm to the operation of the Montana:

Montana | Documents (complete folder&files)
Montana | Garmin | BirdsEye (folder if you don't need it)
Montana | Garmin | CustomMaps (folder if you only use the original Garmin maps)
Montana | Garmin | GPX | Garmin DEMO gpx | (folder and files)
Montana | Garmin | Help (folder and files, except English)
Montans | Garmin | Text (folder and files IF YOU ARE USING THE ENGLISH STD.languarge !!) eventually delete the languages you don't need, the same with:
Montana | Garmin | Voice | (all languages and voices you don't want or need)
Montana | Garmin | Vehicle | (all icon files you don't like)


As for maps, I suggest getting JaVaWa GMTK and Device Manager to see in detail just what maps are where and how big they are, as well as easy backup. I do not own the modern 100K topo, only the ancient one from 1996, so I can't be sure of this, but I have been able to do a partial install of CNNA via BC: Install Maps on Device. I suspect you can also do this for the 100K Topo. This tutorial shows how: http://garminmontanagpsr.wikispaces.com/Send+Map+MapInstall#Choose%20Device

I would NOT delete the basemap!!!! As you will see with Device Manager it isn't very big anyway. A partial install of CNNA (if you have it) and 100K Topo will save over half the space currently used.