How to solve MOSS / Sharepoint 2010 Local Activation permission error (DCOM 10016 error solution)

You may see this error - more than once - when working with your Microsoft Office SharePoint Server (MOSS) 2007 deployment. This animal / error generally shows itself after you have applied an upgrade to an existing deployment. For example, when upgrading from B2 MOSS to B2TR MOSS - or when applying a special service pack from MSFT - you may begin to see a lot of these errors pop up in the SYSTEM event log.
The error CLSID is followed by a class ID for the DCOM+ application that the service account trying to activate that application - does NOT have permission to activate.
For example, let's say I installed MOSS on a server, and used the account mossService as the service account (a least privileged, user account you created to run the MOSS service(s))., when I get this error, I could very well see an error like the following:
The application-specific permission settings do not grant Local Activation permission for the COM Server application with CLSID
{61738644-F196-11D0-9953-00C04FD919C1}
to the user \mossService SID (S-1-5-21-). This security permission can be modified using the Component Services administrative tool.
Copy the GUID following the CLSID above, and Start-->Run-->regedit
With the registry editor open, ensure that your cursor is on the computer at the beginning of the tree (make sure you are not in the middle of some previous edit session in the registry editor).
Edit-->Find and paste in the GUID. It'll stop at the application entry - and you will want to note the application name on the right side pane. In this example, it was the IIS WAMREG admin service that popped up.
Now, open Component Services (typically, from the server - Start-->Administrative Tools-->Component Services), expand Component Services, Computers, My Computer, DCOM Config. Scroll down and find the application (IIS WAMREG in this case). Right-Click-->Properties and select the Security tab. You'll have some options here - the first block Launch and Activation Permissions - ensure that the Customize radio button is selected, and click Edit. Now, add your service account - giving it launch and activate - and in some requirements - remote launch / activate permission.
Restart IIS and continue on. 

NOTE for windows 2008R2 


If you have been installing SharePoint you have probably also seen and fixed the DCOM 10016 error. This error occurs in the event log when the SharePoint service accounts doesn't have the necessary permissions (Local Activation to the IIS WAMREG admin service). Your farm will still function, but your event log will be cluttered.
On a Windows Server 2003 or Windows Server 2008 machine you would just fire up the dcomcnfg utility (with elevated privileges) and enable Local Activation for your domain account.
But for Windows Server 2008 R2 (and Windows 7, since they share the same core) you cannot do this, the property dialog is all disabled due to permission restrictions. It doesn't matter if you are logged in as an administrator or using elevated privileges. The change is probably due to some new security improvements.

The reason for it being disabled is that this dialog is mapped to a key in the registry which the Trusted Installer is owner of and everyone else only has read permissions. The key used by the IIS WAMREG admin is:

HKEY_CLASSES_ROOT\AppID\{61738644-F196-11D0-9953-00C04FD919C1}

Image on the left shows the default permissions for Windows Server 2008 R2 and on the right the default settings for Windows Server 2008.
To be able to change the Launch and Activation Permissions with dcomcnfg you have to change the ownership if this key. Start the registry editor (regedit), find the key, click Advanced in the Permissions dialog of this key and select the Owner tab. Now change the owner of the key to the administrators group for example, then set full control to the administrators group. Make sure not to change the permissions for the TrustedInstaller.
Now you have to restart the dcomcnfg application and once find the IIS WAMREG application and then set the Launch and Activation settings that you need to get rid of the DCOM 10016 error.