Today I attempted to change the identity information for the application pool running my main SharePoint site.
I entered a valid username and password and recycled the application pool – but when I visited my site I got a big error message:
I looked in the system log and found this message:
The identity of application pool, ‘SharePoint – 80’ is invalid. If it remains invalid when the first request for the application pool is processed, the application pool will be disabled. The data field contains the error number.
The event ID for the error was 1021 and the source was W3SVC. To fix this, make sure you are using the proper username and password, and – this is the part I didn’t know about – make sure the user is a member of the ISS_WPG group on the SharePoint server. When you create an application pool through SharePoint’s Central Administration site SharePoint adds the user to that group for you, so you should only have to worry about this if you are changing the identity after SharePoint has created it.
– By Nik Molnar