Why do I get 8000401A errors?

When running a component in an MTS or COM+ application, you may have come across one of the following errors: 
 

ASP 0177 : 8000401a  Server.CreateObject Failed  /<file>.asp, line <line>  The server process could not be started because the configured identity is incorrect. Check the username and password.

 
or 
 

ASP 0178 : 80070005  Server.CreateObject Access Error  /<file>.asp, line <line>  The call to Server.CreateObject failed while checking permissions. Access is denied to this object.

 
The problem is that the 'Identity' set up for the application lacks sufficient privileges. This could be for several reasons, but before we get into those, let's check out where this identity is configured. Open Control Panel, Administrative Tools, and double-click Component Services. Expand COM+ Applications, right-click the application in question, hit Properties, and switch to the Identity tab. You should see a dialog similar to the following: 
 
 
 
One possible reason is that, when setting the identity for your application, you simply chose a user that doesn't have access to the DLL, or to a file or system call the DLL touches. 
 
Another potential cause is that someone changed the Windows password for that user (since the application won't automatically adjust for that change), or it was never entered correctly in the first place. 
 
If this identity is set to the 'Interactive User', then the above error might occur when the user currently logged in to the machine is a peon, or when nobody is logged in at all. This is the primary reason why this error is never detected in development... the user developing the COM+ application, and in complete control of the machine, is also the user logged in and running as the interactive user. 
 
You should make sure to use a local user account with sufficient privileges, if that's what your DLL requires. 
 
See KB #276407 for more information.