Microsoft Silverlight has some problem currently in its installer package,when we try to update/uninstall/reinstall.
Follow steps to remove traces of it,so that reinstall is success.
Step1>Start>Run
reg delete HKLM\Software\Microsoft\Silverlight /f
Step2> Start>Run
rmdir /s /q “%ProgramFiles%\Microsoft Silverlight
Step3>LogOff ,Login again,install Silverlight now.
Step4>It works!