This may happen due to multiple reasons. For example, if your package installation type is one of the following:
- "Per-user only (with administrator rights required)" - on Windows Vista or above, this option creates a package which will be installed per user but requires administrator privileges (e.g. its application files need to be installed in a privileged location such as "Program Files"). In this case, the user may see an "Elevation Prompt Dialog" that will ask for administrator privileges. If the logged user is a member of the "Administrators" user group, he will be asked to allow or deny the installation. Otherwise, he will be prompted to provide the credentials for one of the computer administrators.
- "Per-machine only (fails if the user is not administrator)" - the application will be available for all users on that machine. On Windows Vista or above the user may see an Elevation Prompt dialog that will ask for administrator privileges when installing the package. If the logged user is a member of the "Administrators" user group, he will be asked to allow or deny the installation. Otherwise, he will be prompted to provide credentials for one of the computer administrators.
You can check the installation type of your project by opening your project (.AIP file) and going to "Install Parameters" page (under "Package Definition" group).
This may also happen if you have the "Run as administrator" option enabled in "Install Parameters" page --> under "Installation Options".
Enabling the "Run as administrator" option automatically sets the execution level to "Require Administrator".
Hope this helps.
P.S: I think you forgot to attach the .AIP file (project file), because I can't seem to find it.