Why do we need to use "Classic" mode application pools for IIS 7, when installing Servicedesk and Workflow up to and including version 7.5? Why can't we use the "Integrated" application pool type?
Some of the new features that integrated mode provide, preclude Managed Pipeline mode, which is the reason that Classic mode is required. Also, in Integrated mode you cannot simultaneously use FormsAuthentication and WindowsAuthentication which means auto login with domain user breaks.
For all releases, thru 7.5, all application pools using IIS 7 and later, that are configured for Workflow and Servicedesk, should be configured in Classic mode.
Workflow and Servicedesk Installations up to and including version 7.5