I just installed a new PC in my office. It's an Optiplex 990 running Windows 7 Pro 64bit. I am the System admin and use Remote Desktop Connection Manager. Unfortunately for some reason I cannot install the RDCman.msi package on this machine. I get the following error when trying. This advertised application will not be installed because it might be unsafe. Contact your administrator to change the installation user interface user interface option of the package to basic.