Is there any Cancel option on the window offering the Update and a check box allowing you to never install that update? I know there is a similar option before any updates are downloaded.
Otherwise, allow the update to install and then uninstall it. When it is next offered for download (assuming you change your Automatic Updates options to Notify you of this) use the option I mentioned earlier about canceling the download for ever.
You could also have a look at C:/Windows/ SoftwareDistibution folder.
A general fix for many Window Updates problems is to log on as an Administrator, Stop and Disable the Automatic Updates Service, Rename the folder in C:/Windows called SoftwareDistribution to SoftwareDistributionOLD, Rename the C:/ Windows/ WindowsUpdate.log to WindowsUpdateOLD.log. Restart Automatic Updates Service and set it to Automatic, reboot and let Windows recreate new folder (SoftwareDistribution) and WindowsUpdate.log.