Hi Osama,
The installer may fail due to permission issues or disabled IIS features. I guess you are using IIS7.
Please make sure that you have the optional "IIS 6 Management Compatibility" option installed within IIS7. This installs an API for the new configuration system that is compatible with the old Metabase APIs which FileVista installer uses. You can select this using the "Turn Windows Features on or Off" option in the Control Panel, see the
screenshot.