While installing Silverlight some time you may get an error like The hash value is not correct. You can get more details about the error on clicking the Log File link in the error dialog. This error is coming may be because the setup is unable to download the Silverlight_Developer.exe / Developer runtime failed to download correctly.

The hash value is not correct - Error Screenshot

You can resolve this error by copy / paste the Silverlight_Developer.exe to the “%TEMP%/Silverlight 3.0 Tools folder”. You can download the Silverlight_Developer.exe from here – http://go.microsoft.com/fwlink/?LinkID=150228