To remove a custom activity assembly, you must have administrative permissions on the computer running the Authoring Tool and the computer running the Service Manager console. After the custom activity assembly has been removed, the activities compiled into that assembly are no longer available in personalized activity groups.
To remove a custom activity assembly
On the computer running the Authoring Tool, browse to the Authoring Tool ‘Workflow Activity Library’ folder (for example, D:\Program Files (x86)\Microsoft System Center\Service Manager 2010 Authoring\Workflow Activity Library). Remove the custom activity assembly from this folder.
On the computer running the Service Manager console, browse to the Service Manager installation folder. Remove the custom activity assembly from this folder.
After you have removed the custom activity assembly, notify the Authoring Tool users that the custom activities are no longer available.