How to fix error 0x800F0818 when installing Windows Server SP1

This fix should work on all Microsoft Windows versions that are experiencing error 0x800F0818 when installing SP1.

1. Find CheckSUR.log in C:\Windows\Logs or in a subfolder.
2. Open the log file and find which files under c:\Windows\servicing\packages are corrupted.
3. Download the KB hotfixes that relate to each corrupted package.
4. Take ownership of the packages folder with the following command: "takeown /F c:\Windows\Servicing\Packages /D y /R"
5. Make sure your user has Full Control to c:\Windows\servicing\packages.
6. Delete the .mum and .cat files for each corrupted package from c:\Windows\servicing\packages.
7. Extract the files from each KB hotfix and copy the .mum and .cat files for each package to c:\Windows\servicing\packages.
8. Try installing SP again.

Source