My computer is set to use automatic updates from Windows Update. So when SP1 for Windows 7 came out, I didn't even think about installing it… Windows Update will take care of it for me. But sadly I was mistaking.

After two months I realized that the service pack had not been installed. So I downloaded the service pack from Microsoft Download Center, and tried to install it. But I got an error: "the update is not applicable to your computer".

Googling around, I found that I needed some updates I needed before installing the service pack. I checked Windows Update and indeed the updates were missing. When I checked for updates Windows Update stated that my computer is up to date. Weird. But I didn't gave up… Found the updates from the download center and ran them – but with the same error.

In the event viewer under Setup log I found this error: "Windows update could not be installed because of error 2149842967". Googling it results to nothing. in the System log I found this error: "The TrustedInstaller service failed to start due to the following error: The system cannot find the file specified". The weirdness keep's on going…

TrustedInstaller is in fact a service called "Windows Modules Installer" which is responsible for various processes in the operating system. One of them is Windows Update installations and Windows features installations. Checking the services I so that the WMI service has gone missing. I also tried to open the Windows Features (turn Windows Features on or off in Programs or Features from the Control Panel), but it came out empty. I also checked if the TrustedInstaller.exe exists in c:\windows\servicing folder, but the file wasn't there.

I searched how to recover the service, but the best answer I found was to format and reinstall windows. Eventually I found a similar problem in the Windows Vista forums which offered this solution:

  1. Take the TrustedInstaller.exe from another computer. WATCH OUT: if you have 64 bit version make sure you take the file from a computer with the same version and vice versa. It is not possible to copy the file directly to the c:\windows\servicing folder due to security issues, but it is possible using an installation disk of your Windows 7
  2. Put the file in a temporary folder on your computer
  3. Boot the computer with your Windows 7 installation disk
  4. Click Next in the language selection screen
  5. DO NOT click Install now. Click on repair installation
  6. Select the installation and click next
  7. Select the Command Prompt option
  8. copy the TrustedInstaller.exe to c:\windows\servicing
  9. Exit and restart the computer normally
  10. Run Command Prompt as Administrator (type cmd in the start menu –> right click on cmd.exe –> Run as administrator –> Ok)
  11. Type: cd\windows\servicing
  12. Type: TrustedInstaller.exe
  13. After it finish running go to the services screen (type services.msc and enter)
  14. Find a service called "Windows Modules Installer"
  15. Right click –> Start
  16. From the command prompt type: SFC /scannow
  17. If no issues are found, restart and check for updates in Windows Update

After I did all that I found out that I had about 50 updates to install before installing Service Pack 1. I installed all of them and the service pack.

The lesson: Everybody lies – even Windows Update