Anith Gopal

Issue:  Installation of Silverlight fails with a generic error 1603 “installation failed” after the installation progress shows 99% complete. Cause: To find the root cause open the SilverlightMSI.log from the folder and it shows an error “Cannot create HKEY_LOCAL_MACHINESOFTWAREMozillaPlugins@Microsoft.com/NpCtrl,version=1.0”. This is because a MacAfee ‘Access Protection rule’ has been set on ‘Mozilla & FireFox files and settings’ which blocks Silverlight installer from creating the registry key.

Read the rest here: 
Installation of Silverlight Fails with a generic error 1603 "Installation failed"