Well, i recommend you that you change your server from Microsoft Web Server to a more approriate server for php, such as WampServer. WampServer
WampServer has some configurations you must pay attention to. If you are ever going to install it, make sure to select mysql on the installation process (since it's more compatible with Joomla) and set mysql as your default DBMS after you have installed it. Don't forget to disable/uninstall the IIS.
PS: Do a new installation of Joomla if possible. If you have a custom template, backup your template and, eventually, your database.