When trying to uninstall Microsoft Security Essentials on Windows Vista x86 via Programs and Features, I got an error message, code 8007066F, with no description. How can I remove Security Essentials?

2 Answers 2


The above links didn't work for me, but the response here by GlenDelport worked.

From the URL (with minor modifications):

  • Browse to C:\Program Files\Microsoft Security Client\
  • Locate the file Setup.exe, right click on it and choose properties
  • Click on the Compatibility tab
  • At the bottom of the tab click 'Change Settings for all users'
  • On the next screen check the box for 'Run this program in compatibility mode for:' and choose Windows 7
  • Click OK
  • Click OK
  • From the taskbar search box type cmd.exe and right click and choose 'Run As Administrator'. This will open an elevated command prompt as Administrator
  • In the command prompt window copy/paste or type the following:

    cd C:\Program Files\Microsoft Security Client
    setup.exe /x /disableoslimit
  • Choose to Uninstall

  • Once this has finished, reboot and Microsoft Security Essentials will be gone and Windows Defender should be running correctly.
  • This post was for Windows Vista... Jun 14, 2016 at 5:18
  • Oops. Well, I figure I'll leave this here for now in case anyone has this issue on Windows 10 and receives the 0x8004ff6f error. I'm not sure why I ran into this post and didn't realize it. I'll try to make a different question and delete this post later.
    – Achal Dave
    Jun 14, 2016 at 7:09

Microsoft published a Fixit tool for this at KB 2435760. After running this, Security Essentials was removed, but I still needed to remove the executable from the startup list. I did this by going to Start-> type in MSCONFIG and pressing Enter. Once the MSConfig tool started, I clicked on Startup, and unticked 'Microsoft Security Essentials' from the list.

There is this Microsoft Fix It if the above link does not resolve the issue.

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