To remove old ECS hosts from the ECS configuration drop down menu in CCS Data Collections, please follow the steps below:

1. Please be aware that Domain Admin rights are required to make the following changes.
2. Log in to a domain controller or any machine that has Active Directory Users and Computers.
3. Click on Start  > Administrative Tools > Active Directory Users and Computers. 
4. Click on View in the menu and enable:
   1. Users, Groups, and Computers as containers
   2. Advanced Features
5. Now locate the computer that you no longer wish to be displayed in the ECS configuration drop down menu.
6. Expand the computer. 
7. Select the folder under the selected host that is named ECS and right click and select delete.
8. Complete the steps above for each host that is listed in the ECS configuration drop down menu that is no longer valid.

After completing the process listed above the only hosts listed in the ECS configuration drop down menu should be valid host(s).