How To: Show the 'Editing data in a different coordinate system' warning dialog after it has been turned off
When editing data layers in a map where the feature classes are in more than one coordinate system, or when they are being projected on the fly, a warning appears that states this is the case. It is possible to continue editing, but this may cause feature alignment and snapping problems. The warning dialog box has a check box labeled Don't warn me again. If this box is checked, ArcMap will no longer give the warning.
To show this message again, it is necessary to change the Editor Options settings. Restoring this dialog can be accomplished by doing the following:
Click the Editor drop-down menu in the Editor toolbar, and select Options.
In the Editing Options window, on the General tab, check the check box for Show warnings and information on start editing.
Click Apply, and OK.
ArcGIS 9.x, 8.x
In ArcGIS 9.3.1 and earlier versions, there are two different methods for restoring this warning:
using the AdvancedArcMapSettings utility
making changes in the registry
The first method is highly recommended as it is much safer.
The AdvancedArcMapSettings tool is located in the C:\Program Files\ArcGIS\Utilities folder. Make sure ArcMap is closed before proceeding.
Click the Miscellaneous tab.
There is a Warn when editing datasets with unmatched coordinate systems check box in the Working with data section.
The second method involves editing the registry.
The instructions below include making changes to essential parts of your operating system. It is recommended that you backup your operating system and files, including the registry, before proceeding. Consult with a qualified computer systems professional, if necessary.
Esri cannot guarantee results from incorrect modifications while following these instructions; therefore, use caution and proceed at your own risk.
Close ArcMap if it is open.
Select Start > Run.
In the Open text field, type regedit, and click OK.