The following steps outline the procedure to manually remove a host cluster from the VMM database.   In this specific example, we are removing a two node cluster.   Please note that the GUIDs listed below are specific to this example.   If following these instructions, you will need to determine this same information for your specific environment.   This information can be found in the tbl_ADHC_Host
 
1.       First, stop the VMMservice
2.       Then, take a backup of the existing DB using SQL Management studio. (Right click on DB name, choose tasks, click on Back up, chose a full backup)
3.       Now, right click on table tbl_ADHC_Host and select view or open rows
4.       Click on the SQL button from the tool bar to get the SQL query for the view
5.       In there, start pasting the commands below one by one and verifying they executed correctly. (To execute, you can highlight the command and press F5 or press the “!” symbol)
 
DELETE FROM tbl_ADHC_HostNetworkAdapter WHERE (HostID = '85099616-fdc8-4f85-a702-979a4251f050')
DELETE FROM tbl_ADHC_HostNetworkAdapter WHERE HostID='8cfff5ad-0990-4a92-bd6d-4d24190e5d5a '
DELETE FROM tbl_ADHC_VirtualNetwork WHERE (HostID = '85099616-fdc8-4f85-a702-979a4251f050')
DELETE FROM tbl_ADHC_VirtualNetwork WHERE (HostID = '8cfff5ad-0990-4a92-bd6d-4d24190e5d5a ')
DELETE FROM tbl_ADHC_HostVolume WHERE (HostID = '85099616-fdc8-4f85-a702-979a4251f050') OR (HostID = '8cfff5ad-0990-4a92-bd6d-4d24190e5d5a ')
DELETE FROM tbl_ADHC_HostDisk WHERE (HostID = '85099616-fdc8-4f85-a702-979a4251f050') OR (HostID = '8cfff5ad-0990-4a92-bd6d-4d24190e5d5a ')
DELETE FROM tbl_WLC_PhysicalObject WHERE (HostId = '85099616-fdc8-4f85-a702-979a4251f050') OR (HostId = '8cfff5ad-0990-4a92-bd6d-4d24190e5d5a ')
DELETE FROM tbl_WLC_VObject WHERE (HostId = '85099616-fdc8-4f85-a702-979a4251f050') OR  (HostId = '8cfff5ad-0990-4a92-bd6d-4d24190e5d5a ')
DELETE FROM tbl_ADHC_Host WHERE (HostID = '85099616-fdc8-4f85-a702-979a4251f050') OR  (HostID = '8cfff5ad-0990-4a92-bd6d-4d24190e5d5a ')
DELETE FROM tbl_ADHC_ClusterDisk WHERE (ClusterID = '1148853c-cde3-45d2-82ee-bb04259d6a79')
DELETE FROM tbl_ADHC_HostCluster WHERE (ClusterID = '1148853c-cde3-45d2-82ee-bb04259d6a79')
DELETE FROM tbl_ADHC_AgentServerRelation WHERE (AgentServerID = '648e977e-d10e-40b6-aca2-d9d2dc63b790')
DELETE FROM tbl_ADHC_AgentServer WHERE (ComputerName = 'Server_Node1')
DELETE FROM tbl_ADHC_AgentServer WHERE (ComputerName = 'Server_Node2')
 
       6.    Now start the vmmservice and open the VMM console.

 
http://blogs.technet.com/mbriggs/archive/2009/05/13/how-to-manually-remove-a-host-from-the-vmm-database.aspx