@GSM-Fraggle
I'm assuming you mean City Navigator Europe 2011.40.
If this is the case, the Nuvi 660 WILL NOT recognize the map on SD card.
The 2011.40 map is 2.06GB, the Nuvi 660 CANNOT recognize map files over 2GB.
I had a 670 and tried but did not work.

The 700 series does recognize map sizes over 2GB.
Copy and paste below link, then click on products tab, all the compatible maps will be shown there, the Nuvi 660 is not on list.
[Only registered and activated users can see links. ]

Hope this answered your question.