Dear friends. After reading many posts how to do this and that, here is a easy way that i have unlocked all IMG files, using simple "fast img unlocker" see forum how to use it.
This is to show you how to load maps to your SD card.
Using a card reader on your XP ( windows 7, dont have not tested) with a 4gig card.
I have room to load one map only,
Working are Oztopo 2.1 and Garming topo v3
Just to let you know garmin topo has more offroad tracks, I know i checked out the areas where i go.
1. make a folder called "map" on your desktop
2. copy your prefered map into folder. Call it gmapsup2.img
3. now copy whole the folder with the map inside to your SD card. I USED MY PC CARD READER. UNTESTED IF COPYING DIRECT VIA CABLE LINK THRU NUVI TO CARD.
4. Turn OFF your NUVI by holding the button on top right for about 5 second until you get option to turn off.
5. Incert your sd into slot...turn nuvi on....go to tools/settings/mymaps. YOU should have all your normal maps there including your new map, that will show the map name EG: Oztopo 2.1
IT WORKED FOR ME ON BOTH MAPS, BUT I HAD TO DELETE ONE MAP TO FIT OTHER, HAD NO PROBLEMS...note. while nuvi is loading for power up look at bottom of screen and if shows "loading map" thats a good sign.
EXTRA. to run your TOPO maps properly...UNTICK other maps that came with your nuvi.
What i done is.. ticked topo map and left CN 2011.30 3D running. If you leave CN & NZ ALL running you wont see the topo maps and contour lines.
UNTESTED. voice command and on road navigation.
If someone has done this can you please post for others.
This is all i know , its been done by trial and error, I found that there are way too many confusing and ways to get maps on garmin devices, this is the easiest way possible i know.