Source: Microsoft-Windows-WindowsUpdateClientĭescription: Installation Failure: Windows failed to install the following update with error 0x80070643: Microsoft Security Essentials Client Update Package - KB2691905. Searching through the event logs reveals other errors, which I will list here in the hope that it helps other Googlers Of course, clicking on the 'Get help' link is of no help at all.Īpparently, the code '0x80070005' means 'Access denied', but there is no way to find out to what the access was denied.