You can also download software from "Sendmap" and then down load mapping from emerald-island.eu and load it to your unit, it really is very simple and it works and its free!!
http://emerald-island.eu/wikka/EmeraldIsland How to install Mapsets on a Garmin usb compatible GPS device
Download and install Sendmap20 fromhttp://www.cgpsmapper.com/download/sendmap20.zip
Create a folder on your desktop called “Maps”
Download the file “Irelandmap189setup.exe” from http://emerald-island.eu/
to your desktop
Doubleclick the file “Irelandmap189setup.exe” or new version
Follow the instructions and when asked browse for the folder “Maps” on your desktop.
On the next screen select the default “Full Installation option”
On the next screen select “Install”
The data files are now extracted to the “Maps “ folder.
Click the “Finish” option, close the information notice that opens.
Connect you GPS to you PC using your usb cable.
Open the “Sendmap” program.
Click the “Add maps” button
Browse to you desktop and open the “Maps” folder you have previously created
Open the folder called “img”
Select the 6 files numbered 10000101 to 10000106 with the extention .img only by dragging a box over them then click on the “open “ option. ( I had to leave out files 3 and 4 to get this to work but it has all the relevant info for walking)
The 6 files will appear in your window in the “Sendmap” program.
Click on the “Connect” button and you should see your GPS units name appear below the button.
Click on the “Upload maps to GPS” button in the bottom left .
The maps will be sent to your GPS
You will now have a 6 layered mapset on your map view screen in your GPS.
You can adjust the detail / settings with reference to your GPS instruction book.