In CAPC, under Monitored Devices, choose the search field.
Put your device name in the search field.
Click on the search button.
Now you will see the device name with a check box next to it.
Check it and click on delete. Or right click and choose delete.
This device will be removed from the associated Data Aggregator.
If the element exists in any other datasource, it will still show up in CAPC. Repeat the same steps for each datasource if you would like to delete the element completely from CAPC.