I am having the same trouble installing Service Pack 1, but none of the above seems quite to cover my experience. I am running Windows 7 Enterprise N and When I try to install SP1 using Windows Update I get the Error Code 9024200D. I have followed the links from the help popup and installed and run both MicrosoftFixit50123 and the System Updates Readiness Tool Windows6.1-KB947821-v22-x86, but I still get the same result. It is a recent install of Windows 7, I do not use AVG or any registry cleaner, and other Windows Updates, including more recent ones, have installed perfectly.
Any suggestions, please?