The global Administrative area database has been developed by a group of zoologists and agricultural scientists in California.
GADM download--Global Administrative Areas level 0 is 150 MB, level 2 is 184 MB. National (level 0), State/province/equivalent (level 1), and County/district/equivalent (level 2), and smaller Level 3.
There are political questions about boundary locations, which are not clearly demarcated on the ground. While most of the world's boundaries are clearly agreed to by the countries they separate, there are a number of disputed boundaries such as Kashmir, the Gaza Strip, the West Bank, or the Golan Heights. For these, if you go to a place like Google Maps, you will see boundaries drawn with a different symbology. In some cases you might see different boundaries or symbologies based on the country you are in. The same can be true for the names displayed.
GADM does not mention this challenge, and you will have to look at the boundaries to see how they handled the disputed boundaries. For example, they have a "Palestina" "country". NGA has the following note about its gazetteers: " The geographic names in this database are provided for the guidance of and use by the Federal Government and for the information of the general public. The names, variants and associated data may not reflect the views of the United States Government on the sovereignty over geographic features." NGA has country files for the "Gaza Strip" and "West Bank"
Using GADM in MICRODEM
Overlay, GADM will take you straight to the correct directory if you have the global GADM in the correct locations (subdirectories c:\mapdata\gadm\adm0 and c:\mapdata\gadm\adm1). This will avoid having to navigate to the correct directory. This will be higher resolution that the World boundaries from Natural Earth, and goes down to lower levels.
Alternative: GAUL, Global Adminiatrative Units Layers, from UN's FAO: http://www.fao.org/geonetwork/srv/en/metadata.show?id=12691
Last revision 3/1/2018