How to solve the Windows 7 SP1 800F0A12 / 0x800F0A12 Update Error

Roughly two weeks ago Microsoft released Windows 7 Service Pack 1 to the general public. As is standard practice for most IT departments I held off on rolling out Windows 7 SP1 until any issues with the update had been identified. Since no issues have been identified that would affect the systems I manage I began rolling out the update this week. Unlike many of Microsoft’s previous operating system service packs, Windows 7 SP1 serves primarily as a roll-up of previous security updates. Still, there are a few updates included in SP1 that people will want to take advantage of — many of which are performance related. For whatever reason the update to SP1 hasn’t been as smooth as previous service packs. From what I’ve read on the interweb the installation of SP1 has become downright frustrating for many.

In many cases the update attempt simply ends with a vague error, Update error 800F0A12. I encountered this error on several computers I attempted to update. When I first experienced an installation issue I followed the normal troubleshooting steps. Disable anti-virus. Ok, I know, why didn’t I disable it to begin with? Well the simple truth is that most anti-virus solutions no longer interfere with software installations or OS updates. Unfortunately disabling anti-virus had no effect on resolving the error. Next step — Check for free space on the boot partition. Check — I had plenty of free space. Lastly, check for software that may be locking the disk and preventing the update from completing successfully. Nope, no software was present that could interfere in that manner. So now I was out of ideas. That was until I stumbled upon this article. Windows 7 utilizes a small system partition. This partition was not being automatically mounted and as a result the update to SP1 was failing. All I had to do was open a command prompt, running it elevated as Administrator, and type “mountvol /E” at the command prompt. Then I rebooted and voila — SP1 installed without a hitch. This same solution solved the error on all the computers I encountered the 800F0A12 error on.

If you experience difficulty installing Windows 7 SP 1 follow these troubleshooting steps.

For more information see this article:

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19 Responses to How to solve the Windows 7 SP1 800F0A12 / 0x800F0A12 Update Error

  1. If you receive Windows 7 installation error: 0x800F0A12 while installing Service pack 1 on Windows 7, it simply means that SP1 installer cannot access Windows system partition of the computer’s hard disk for updating files. Go through following step-by-step instructions:

    ->Click ‘Start’ and type: ‘command prompt’ in the search box.

    ->When results appear, put right-click on ‘Command Prompt’. Go to ‘Run as Administrator’.However, if you are further asked about administrator confirmation details, give required username and password.

    ->Type ‘bcdedit’ and press ‘Enter’.

    -> Note the error messages you receive and take relevant steps to overcome each. Following are the errors that may appear:


    ->Error reads ‘The boot configuration data store could not be opened. Access is denied’.

    -> You might have gone in the command prompt with administrator privileges. Go on repeating the steps again and select ‘Run as Administrator’ given in step 2.


    ->Error reads ‘The boot configuration data store could not be opened. The system cannot find the file specified’.

    ->Click ‘Start’. Type: ‘command prompt’ in the search box.

    ->When results appear, put right-click on ‘Command Prompt’. Go to ‘Run as Administrator’. However, if you are further asked about administrator confirmation details, give required username and password.

    ->Type: ‘mountvol/E’. Press ‘Enter’.

    ->Restart you system and give one more attempt to install SP1.

  2. Same issue as Sprewell. I’m dualbooting Windows 7 and Ubuntu 12.04, and this is the first time I got this error message. I tried “mountvol /E” but it didn’t work. I then read Sprewell’s comment and changed the hard drive order in the boot sequence from BIOS, and it worked. I’m using two SSDs, one with Windows 7 and one with Ubuntu. So just make sure Windows boots first.

      • this works

        here’s the relevant answer:-

        You can also change the grub default boot entry from the command line without having to install any additional tool. This won’t change the order in the list but it will allow a different OS to boot by default, which sounds like what you may want anyway.

        First, make a backup copy of /etc/default/grub. In case something goes wrong, you can easily revert to the known-good copy.

        sudo cp /etc/default/grub /etc/default/grub.bak

        Then edit the file using vim or the text editor of your choice.

        sudo vim /etc/default/grub

        Find the line that contains GRUB_DEFAULT=0 and set it to GRUB_DEFAULT=x where x is the index of grub menu item to which you would like to boot to by default. Note that the menu items are zero-indexed. That means that the first item in the list is 0 and that the sixth item is actually 5. So to boot to the sixth item in the list, the line would read GRUB_DEFAULT=5.

        Additionally, if you want to use a kernel in the “Previous Linux Versions” menu, you’ll want to change GRUB_DEFAULT=0 to GRUB_DEFAULT=”2>x” (make sure to include the quotations), where x is the placement of the old kernel on the sub-list (assuming the “Previous Linux Versions” is third on the main list). Remember that the list always begins counting at 0.

        Then build the updated grub menu.

        sudo update-grub

  3. Same solution as Sprewell. I am dual booting a hackintosh build on a separate disk. Just unplugged the power from the OSX disk and everything installed fine.

  4. I ran into another variation of this bug when trying to install SP1. I have two disks with multiple operating systems installed, so I boot from an IDE disk with my bootmanager installed, then run Windows 7 from a SATA disk off a single partition. It turns out that Windows 7 gets confused by the fact that the IDE disk is the main boot disk with its own active partition, so it apparently looks in the active partition on the IDE disk and errors out when it doesn’t find the boot config data it needs for SP1 there. I was able to get it working by disabling the IDE disk in the BIOS, I now notice that simply changing the boot disk order in the BIOS also appears to work.

    I had a similar issue when I was installing Win7 to the SATA disk, where it would let me choose the partition but wouldn’t install to it. When I hit Shift+F10 to drop to a command prompt and check the Setup log files, there were repeated errors saying “The selected disk is not the computer’s boot disk.” I read online that the installer gets confused by other disks, so I worked around that also by unplugging the IDE disk, seems like a similar problem. Looks like Microsoft is really pushing the single OS install, considering it would be straightforward to put in logic to handle these other cases also.

    • @Sprewell-
      Hear, hear! I had the same update problem as everyone on this thread, but most of the solutions were about making one *partition* on the physical drive active. I set up my dualboot on two separate hard drives, so there’s only one partition on my dedicated Windows drive. None of these solutions did the trick, but yours did. In my case, at the BIOS screen I hit F12 (Gigabyte motherboard) to select boot drive (faster than changing boot order). Windows booted directly, rather than through Chimera/Chamelon bootloader on my OSX drive… and the rest was smooth sailing. Thanks!

  5. also ensure the system partition is active.

    to activate do the following:

    1. Start->Administrative Tools->Computer Management
    if you don’t have “Administrative Tools” enabled, do
    Start->Run… and type “compmgmt.msc /s” in the input box
    If you don’t have “Run…” enabled, right-click on the toolbar, click on “Properties”,
    click the “Start Menu” tab, click on “Customize…”, scroll down to where it says
    “Run command”, click the box next to it and ensure the box is now checked. Then
    click “OK”, and “OK” again.
    2. On the left-hand side, open up “Disk Management” (under “Storage”) by clicking on it.
    3. On the list in the center panel, right-click the list item that reads “SYSTEM”, and click
    the “Mark Partition as Active” item. If it is greyed-out, the partition is already active,
    so this won’t help with your problem.
    4. Exit Computer Management and retry your SP1 install.