This Knowledgebase article provides information about resetting the IUSR_<machine name> and IWAM_<machine name> passwords.
During normal installation of an Internet Information Server (IIS), the IUSR_<machine name> and IWAM_<machine name> passwords are set automatically during the installation process.
In the event that the IUSR_<machine name> and IWAM_<machine name> passwords must be reset or changed, and the IIS server is protected by Neverfail Heartbeat, than the reset or change of the passwords must be performed on all servers within the Neverfail Heartbeat Cluster regardless of the server's role (active or passive).
All IIS versions installed in IIS6 compatibility mode
Neverfail Heartbeat all versions
Neverfail for IIS Plug-in v201.5.4 and later