ArcGIS Explorer 2012 can be run off of an external USB connected drive. To do this install ArcGIS Explorer on a computer, then from the installed location copy the Explorer or Explorer (86) folder and all of its contents to the USB drive. From the USB drive you can launch ArcGIS Explorer by double clicking on the e3.exe in the Explorer (x86)\bin folder. This allows you to run ArcGIS Explorer without installing it on a computer. You could also put your ArcGIS Explorer map and all data on the device, creating a portable mapping solution. Be sure to use relative paths for local data. You may also want to look into mapping your USB drive to a specific letter.
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