Here's a handy quick fix if anyone is getting the ERROR 01009 warning when they try to use extensions from ArcToolbox (e.g. Spatial Analyst)
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TOOL NOT LICENSED
Unable to execute the selected tool.
You do not have the necessary license to execute the selected tool.
ERROR 010096: There is no Spatial Analyst currently available or enabled.
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In ArcMap 10.1
Select Customize (from the top of the screen)
In the Customize menu, select Extensions
Check the Extension (Spatial Analyst)
* Spatial Analyst is now enabled and you should not get that message any longer (provided you already had it setup correctly in Administrator)
- hopefully that saved a few headaches for future ArcGIS students -