Recently I had to downgrade a SQL Express instance from the 2008 version back to 2005. The downgrade solved my DB performance problems, but created a monitoring problem. Operations Manager continued to believe that this server was running SQL 2008!
So, how do you get rid of a monitored object that is part of a dynamically discovered group? The answer lies (as with most OpsMgr problems) in overrides:
Boris of OpsMgr++ fame tells us to use the “Authoring” view in the OpsMgr console to find the “Object Discovery” rule that found your SQL instance (probably “SQL 2008 DB Engine”). You then generate on override which will disable discovery for your named computer. Since SQL discovery runs fairly infrequently, you may also want to override the same rule for all computers, forcing discovery to a more frequent interval (say… 300-600 seconds).
After discovery completes, open the OpsMgr PowerShell console, and run the “Remove-DisabledMonitoringObject” cmdlet (with no arguments). If you are exceptionally lucky, your undesired object will disappear from the OpsMgr Monitoring view in short order.