Enable user to browse for source while elevated
Computer Configuration\Administrative Templates\Windows Components\Windows Installer
Allows users to search for installation files during privileged installations.
This policy enables the Browse button on the Use feature from dialog box. As a result, users can search for installation files, even when the installation program is running with elevated system privileges. By default, only system administrators can browse during installations with elevated privileges, such as installations offered on the desktop or displayed in Add/Remove Programs.
Because the installation is running with elevated system privileges, users can browse through directories that their own permissions would not allow.
This policy does not affect installations that run in the user's security context.