The update ‘KB 947821’ is for System Update Readiness tool. I would suggest you to download and try to install it. You need to choose the correct download file according to the version of windows installed.
Note To install the correct version of System Update Readiness Tool, you must know what version of Windows that you are running.
You can download this update manually from the link: http://support.microsoft.com/kb/947821
Once you have run this readiness tool successfully, reboot the computer and then click on check for updates one more time.
