How do you delete a map

How did you install it? The Garmin map update overwrites the old maps.

I installed it with a CD, On my unit the map Info shows 2 maps 1. City Navigator North America NT 2008
2. CN North America NT 2010.40
Their's a box net to each map that you can put a check mark in. All new roads are in the map for #2, If I but a check mark in # 2 only then the new roads show up, but if I put a check mark in # 1 only new roads don't show up. It didn't ovwrwrite the old map..

Sounds like you installed 2010.40 in an external SD card. Therefore you have 2 maps, 2008 in Nuvi internal memory and 2010 in the SD card. Best thing to do is to ignore the message or you can reinstall 2010.40 from your computer to Nuvi internal memory. If you do it this way, 2010.40 will overwrite 2008 map.

I don't have a external SD card

Is it possible that you have and installed the full new version of City Navigator on DVD and not the cheaper upgrade version meant for folks who already have maps installed? The upgrade version will overwrite the old map on your GPS leaving only the new one. If you have the full version DVD, my guess is that it installs its map but doesn't overwrite existing maps.

Plug the Nuvi into your PC and go into the Nuvi drive. Under the Garmin folder, look for files named gmapprom.img and gmapsupp.img. Do you have both? Are both approximately 1 GB in size? If so, your 660 probably has 4 GB of FLASH memory, and that's why both maps fit at the same time. You can probably tell which is the newer map from the timestamps. Backup both files on your PC so you can restore them if necessary. If the gmapsupp.img is the older file (unlikely), just delete it. If the gmapprom.img file is older, delete it and then rename gmapsupp.img to gmapprom.img. Disconnect and check your map info again. In case of trouble, just restore both files and live with the message. Good luck.

used Garmin Cd City Navigator NT North America 2008.
Used the map upgrade 2011_10 with this program.It fixed the problem.