When you go through the CSG configuration service wizard, you can view the historical csg certificates which are no longer reequired.

To remove:

1) Logon to the CSG server
2) Click start
3) Click run
4) Type mmc and click OK
5) Click file and add/remove snapin
6) Click the add button
7) Select certificates and click Add
8.) Select Computer Account, click next and finish
9)  Click Close and then click OK
10) Expand Certificates (local computer)
11) Expand the folder named Personal and click Certificates
12) All certificates will appear. Take a backup of any old certificates just incase and do not delete the new certificate.