When installing the Web Thin Client on Vista, Internet Explorer will prompt for permission to install the web thin client activex control. Even though permission is granted the Web Thin Client will not properly install due to Vista's UAC.
Thin Client and Web runtime Installations
Vista's UAC mechanism blocks the installation of ActiveX controls, such as Acucorp's Thin Client, onto systems that are not running Internet Explorer 7 in administrator mode.
To run in administrator mode right click on the IE7 shortcut and select "Run as Administrator".
Vista also includes an ActiveX installer service that allows IT administrators to use Group Policy to specify Web sites from which standard users will be allowed to install ActiveX controls.