How to remove a incorrect monitoringobject

Hi,

I am using SCOM 2007 R2 version 6.1.7221 and have two alerts for two objects that do not exist(IE in this case there is no drive E: on the server reported so hence the diskfree fails). This is causing the powershell script to fail and raises an alert. The alert gives me the GUID of the monitoringobject, the instance name is 'Instance name: Log Disk E:(serverFQDN)' that the script is trying to exceute. The alert is from the Micosoft Exchange MP for diskfreepercentage.

Please can you explain how do I go about removing this monitoringobject?