When I run the installation file for the Silverlight Developer Runtime x64 (http://go.microsoft.com/fwlink/?LinkId=229324), it unpacks the files, then displays the installation splash screen allowing me to click "Install Now". Once I click "Install Now", it pops up a dialogue asking for the location of "silverlight.msi". If I browse to the unpack directory (on my machine its d:\<long alpha numeric string\") I can manually select the "silverlight.msi". When I then click "OK" to continue, I am prompted with the message "The file <silverlight.msi I just selected> is not a valid installation package for the product Microsoft Silverlight. Try to find the installation package 'silverlight.msi' in a folder from which you can install Microsoft Silverlight."