if its not reportig, then just right click on it and select delete. or
Follow this step so that It does not report to SEPM any more
1) Create a new group in SEPM.
2) Move the client to the new group
3) Click on the new group and select Details tab ( one on the top right next to policies)
4) Note down the Policy serial number it will alpha numberic like ( 4B55-06/26/2014 14:13:09 162)
5) Navigate to SEPM installed drive < Drive>
\Program Files (x86)\Symantec\Symantec Endpoint Protection Manager\data\outbox\agent
6) Search for the folder which begins with the policy serial number ( from Step 4)
7) Open the folder
8) open the sylink.xml file in a wordpad, Change the ip address or just scrap it or just put a blank Sylink.xml
9) Save it
Next time when the client talks to SEPM, it will download this blank sylink file and it wont be able to communicate.