You are logged into a machine to use ArcIMS, but you are not the user that installed ArcIMS. When you open ArcIMS Administrator the Site Properties dialog opens and asks you to input hostname, hostname alias, website, output, and so on.
You complete this information, but when adding a new service, no output alias or path for Image Services is given. Site Properties shows the correct properties.
The setup stores the necessary configuration information to use the applications in the \profiles\username location of the user that installed ArcIMS.
Copy the aimsdefaults.properties file from the profiles\username folder of the account that installed ArcIMS to the \profiles\username folder of the alternate users.
It is important to copy the file that resides in the installer's profile folder. It will update during the initial installation. The aimsdefaults.properties file located in the ArcIMS\Common installation location contains default values and will not work.
Alternatively, if you are logged in with administrator privileges, run the Post Installation setup again. Select Custom, check the ArcIMS configuration option, uncheck all others if necessary, and complete the necessary information.