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Thread: Defender won't turn on

  1. #1
    Corey Guest

    Defender won't turn on

    In Windows Security Center, it shows that Defender is turned off. When I
    click to turn on, it searches for new defintions...but none are ever
    found...and Defender will not turn on. However, in the Application Event
    Log, there are numerous events with Defender as the source showing scans
    being done each night along with other detection activity. I'm running Vista
    Home Premium w/ NAV2007...both were pre-loaded on a new PC from Dell.

    Any insight as to why Security Center shows Defender as off is appreciated
    along with how to resolve.

  2. #2
    Luke Guest

    RE Defender wont turn on

    I have this same problem. It is driving me crazy. Anyone found a way to fix this?

  3. #3
    Mohit Kapoor Guest

    RE: Defender won't turn on

    Please perform the following to resolve your issues.

    Open elevated command prompt and type cd\windows\system32\wbem press enter

    Then type ren repository repository.old and press enter.

    Restart the computer and check your security center again hopefully
    everything should be working there.

  4. #4
    Joe Guest
    I recieved a " Access is denied" message when I followed these instructions.
    I ran the command prompt as adminsitrator and recieved the same message.
    Vista Home Premium.
    Windows Defender will not turn on, and doesn't recognize Avast (free

  5. #5
    Mohit Kapoor Guest

    Re: Defender won't turn on

    Simple All you need to do is

    Start->Search type cmd and command prompt will show up->Right click->Run as
    administrator and then type the commands as follows

    Cd c:\windows\system32\wbem
    ren repository repository.old press enter and reboot

    If this doesn't help start the computer in safe mode and rename the folder
    in safe mode.

    If it still doesn't works turn off UAC and then try to rename it with
    elevated command prompt in normal mode.

    If it still doesn't works up then right click on the repository folder under
    c:\windows\system32\wbem and go to properties ->Security Tab->Click
    advanced->Ownership->Check replace owner on the subcontainers and
    objects->Select your user name or administrators and click apply and then
    Then click add (In the security tab) and then on the next window type
    everyone and click OK.Ensure to give all permissions to everyone and click OK.

    Rename the folder now.

  6. #6
    Steve Guest

    Re: Defender won't turn on

    I have the same problem. Thanks for the clear instructiuons.

    I tried every step outlined in your post and still cannot rename the
    Repository Folder.

    After the last step to change owner and give everyone permissions, I still
    get "You need permissons to perform this action" from Explorer or "access is
    denied" from an elevated command prompt

  7. #7
    Steve Guest

    Re: Defender won't turn on

    Found this information

    which suggests two ways to resolve this.

    One is to stop Windows Management Instrumentation with

    net stop winmgmt

    before renaming the repository folder

    then starting it again with

    net start winmgmt.

    This allowed me to rename the folder and once the folder was renamed, the
    original problem of Security Centre and Windows Defender being incorrectly
    reported as off was fixed.

  8. #8
    Mohit Kapoor Guest

    Re: Defender won't turn on

    Kindly confirm me who is the current owner of your repository folder.

    Just confirming the correct procedure again

    Right click ->Properties->Security tab->Advance Button->ownership tab

    Further have you done an upgrade or it's a clean install?

    Thanks and Regards

  9. #9
    Steve Guest

    Re: Defender won't turn on

    The owner was Steve\Administrator and this was an upgrade to Vista Business
    from XP Professional SP2 with WIndows Defender already installed. However as
    posted above stopping the Windows Management Instrumentation service allowed
    the folder to be renamed which then solved the problem.

  10. #10
    stephan Guest
    This worked for me, after rebooting, everything was turned on !
    thanks alot.

    Is the Defender service set to Automatic?

  11. #11
    snuffy Guest

    RE: RE Defender wont turn on

    Snuffy wrote: Defender will not turn on when I boot up , but I have to turn
    it on thru control panel.

  12. #12
    Join Date
    Jul 2009

    Re: Defender won't turn on

    Try this to manually install updates of windows defender, It should work!

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