Windows 7 SP1 installation fails with error 0x800f0818

I came across a peculiar problem today trying to install SP1 on a Windows 7 laptop. Whenever I ran the Windows 7 SP1 installer or tried to update to SP1 using Windows Update the installation failed with a cryptic error ‘0x800f0818‘. I tried various things such as running sfc /scannow and installing the Windows 7 System Readiness Tool (64 bit in my case), but neither reported problems.

After a bit of digging I found an entry in the CheckSUR log file found in C:\Windows\Logs\CBS which seemed to be related. In this case a .Net Framework update had failed to install a few times and this particular update was referenced in the log file:

Checking Windows Servicing Packages

Checking Package Manifests and Catalogs (f) CBS MUM Corrupt 0x00000000 servicing\Packages\Package_for_KB979916_RTM~31bf3856ad364e35~amd64~~  Expected file name Microsoft-Windows-Foundation-Package~31bf3856ad364e35~amd64~~6.1.7600.16385.mum does not match the actual file name

Checking Package Watchlist

Checking Component Watchlist

Checking Packages

Checking Component Store

Summary: Seconds executed: 485  Found 1 errors   CBS MUM Corrupt Total count: 1

Unavailable repair files:  servicing\packages\Package_for_KB979916_RTM~31bf3856ad364e35~amd64~~  servicing\packages\

To fix the problem I had to remove entries for the corrupt package from the registry (IMPORTANT: taking a backup first) from:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Component Based Servicing\Packages

The specific entries are shown below. There are two, the highlighted entry, and the one beneath:

Deleting corrupt package entries from the registry


After deleting the two entries I reran Windows Update checking for updates and this package was redownloaded and then installed without issue. After this the service pack 1 installation proceeded without error. You may find that the specific update referenced in your CheckSUR log is different to the one mentioned here, but the method is the same.

Allow popups from certain websites using a group policy object

If you need to allow pop ups from specific websites when using Internet Explorer in your environment, you can enable them by using the ‘Pop-up allow list’ setting in the relevant group policy object (GPO).

Simply edit the relevant GPO, adding the addresses of web sites that you wish to allow pop ups for. The setting can be found under:

Computer Configuration, Administrative Templates, Windows Components, Internet Explorer, Pop-up allow list


User Configuration, Administrative Templates, Windows Components, Internet Explorer, Pop-up allow list

Allow pop ups in Internet Explorer using the ‘Pop-up allow list’ setting in a group policy object