Script-based tools fail to execute with background processing enabled when ArcGIS Engine is installed

Description

Geoprocessing tools based on scripts do not execute when background processing is enabled and ArcGIS Engine Runtime has been installed on the same machine.

After executing the tool, the Results window shows an executing and start message, but nothing further. The status changes to a red 'x'.

Cause

ArcGIS Engine Runtime can run tools in the background, similar to ArcGIS for Desktop. When ArcGIS Engine Runtime was the last product installed, it binds to the background processes, which makes them unusable by ArcGIS for Desktop.

Workaround

• If ArcGIS Engine Runtime was the last application installed, run a repair on the ArcGIS for Desktop installation. The repair will rebind the background processes to the Desktop product.
  
  A repair can be performed from the Control Panel > Programs and Features menu. Select ArcGIS Desktop and click the Modify button. Choose the repair option and proceed.
• Change the order of installation.
  Installing ArcGIS for Desktop as the last product properly binds the background processes.
• Uninstall ArcGIS Engine Runtime from the machine.