Configure Service Account not working in Central Admin

Hi,

I am in need of urgent help.

The App Pool identity account (domain\spapppool) for a web application in SharePoint most probably got deleted from AD.

So, the web app was not working. Someone changed the identity to a new service account but did not follow the best practice of changing it through Central Admin. He/She changed it through IIS.

Now, the Configure Service Account is not working. When I try to delete that account domain\spapppool using central admin's configure managed account or using powershell, it gives me the error that this account is used in app pool for the site and also some other sites (web apps) .

So now what can I do to get Configure Service Account back. Please help as I cannot access my web app because of this.

thanks,

sangswiss