.nmc extension

[ReneeRafferty]

I have downloaded a Gulf of Mexico basemap from the ArcGISonline:  GOM_Fields_In_Play.nmc.  The info states that this is for ArcExplorer. 
When I open ArcExplorer9.3.1 is does not read .nmc extensions.  It is looking for an .axl extension.  But conversely, if I click on the .nmc file it asks me which software I want use to open it and lists my ArcView, but not the ArcExplorer.  Ultimately, I am trying to download a basemap layer showing the topography/bathymetry for the GOM only

[ShellyGill2]

Hi there,

ArcGIS Explorer does read .nmc files, and you can download it here:
http://www.esri.com/software/arcgis/explorer/index.html

There is a different viewer application called ArcExplorer, I think this may be the one you have installed:
http://www.esri.com/software/arcexplorer/index.html

The names are very similar... it's not ideal, and I can understand why the two can easily be mixed up.