If you want full control use
Google Maps API using Flash[
^], once you get the data using this control, store it on your custom database and use it.
For a quick ready-made control
GMap.NET - Great Maps for Windows Forms and Presentation[
^] - This supports offline mode also
but in both the case you want to check the Google License for using Google Map API, it's not free unless your software/service is also completely free. you cannot use it for commercial purpose.
or consider using Open Street Map, it's free.