COM+ 1.5 (provided with Windows XP) has an interesting feature that is missing in COM+ 1.0: the ability to disable entire COM+ applications or just their individual components. You can disable and re-enable a COM+ application or component by right-clicking on it in the Component Services MMC explorer and selecting the Disable menu command. A disabled application or component is marked with a little square besides it.
All clients attempting to launch a disabled application or create a disabled component will receive an error, so this is a simple way to test how client apps behave in such a case. Interestingly, however, all clients that were connected to the application before it was disabled will continue to run correctly, so an administrator can use this feature to gracefully shut down a COM+ application without affecting any client that is using it.
Notice that only COM+ 1.5 applications can be disabled, but legacy apps can't. For this reason you might not find the Disable command menu associated with some items in the COM+ explorer.