Changing service account passwords - The Service is unavailable
Problem: Browsers return the following error "Service Unavailable Http Error 503. The Service is unavailable." on all SharePoint websites including central admin.
Initial Hypothesis: I changed my password yesterday causing the app polls to fail when logging in. The domain account used on my development machine required a password change. Starting the machine causes all the IIS web sites to display the error message "Service Unavailable". I run various services and application polls using my domain account. The services can no longer log on. Application pool cannot be started after the reboot/iisreset.
Resolution: Change the log on details for the application pools used by IIS that run using the domain account that's password was reset. Also start the Windows services that run using the windows domain account.