Once in a while you will encounter a situation where you will have to uninstall the agent from a command line. For instance if somebody shutdown a SCOM test environment while forgetting to do the uninstall of all agents first. They will all be active and pointing to a non-existing server and giving errors and trouble. So here are some ways of removing an agent if you cannot use the SCOM console for instance to uninstall them.
Agents: remove configured management group or uninstall agent using command line
http://blogs.technet.com/b/jonathanalmquist/archive/2009/12/30/agents-remove-configured-management-group-or-uninstall-agent-using-command-line.aspx
Brute Force Uninstall of Management Group
http://blogs.technet.com/b/jonathanalmquist/archive/2010/07/22/brute-force-uninstall-of-management-group.aspx
Windows Agent Install MSI Use Cases and Commands
http://blogs.technet.com/b/momteam/archive/2009/07/08/windows-agent-install-msi-use-cases-and-commands.aspx
If you are trying to remove or change an agent through the manual route from a machine by using the add/remove programs option you might also run into errors, especially on Windows 2008 servers: Microsoft ESENT Keys are required.
https://blog.topqore.com/2010/05/07/scom-agent-error-microsoft-esent-keys-are-required
