Hi I hope this is the correct group to post this.I have installed HMC 3.5 about 90% complete, but when trying to install "Web Services" it fails with the error :"MSI log returned non-zero error code 1603"Event Viewer - System shows w3svc error "the identity of application pool, 'MPFClientAcctPool' 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."What can be causing this?RegardsTony

Hello Tony, This is Exchange Server - Admin forum, suggest you to post your query in Hosting forum to get better responces from product experts. Microsoft Solution for Hosted Exchange Forum: http://forums.asp.net/159.aspx