We have upgraded an 800xA system from SV5.1 to 6.1 and migrated to a new domain. Now we have ghost 800xa service account from the old domain in the system, which cannot be deleted neither from the Configuration Wizard nor from the System Configuration Console? Is it safe to just delete it from all User groups in the User structure in Plant Explorer?
The service account and the account used to create the system become protected against acccidental deletion by being equipped with a "key". One of the aspects (IIRC the User Aspect) on the user object has this key named "Service Account Key" which can be deleted. The key is to be found in the aspect details which you can call by right clicking any aspect and select Details... Once the Service Account Key has been removed, the user can be deleted.
TBH, there has been some issues in this area lately, so you might have to contact your regional ABB support center for advise if you should fail with the above.