Home > windows 7 > Windows 7 SP1 RTM Installation Error 0x800F0A12

Windows 7 SP1 RTM Installation Error 0x800F0A12

According to some reports, attempting to install Service Pack 1 RTM on top of Windows 7 or Windows Server 2008 R2 can produce the following error message: 0x800F0A12 accompanying the failure of the deployment process.

Microsoft explained that the exception is caused because the SP1 RTM installer finds it impossible to access the system partition that Windows 7 and Windows Server 2008 R2 build.

No access to this portion of the HDD means that the files contained cannot be upgraded with the new resources featured by Service Pack 1.

By default, during installation, both Windows 7 and its server counterpart create a 200 MB system partition on the hard drive, which is not accessible through Windows Explorer.

However, both platforms can still leverage the system partition even though end users cannot browse its contents.

Microsoft explains that there are a few reasons why this area of the HDD can become inaccessible, leading to such issues as SP1 RTM installation error 0x800F0A12.

The software giant enumerated a total of four reasons:

“•The system partition isn’t automatically mounted, or made accessible to Windows, during startup.

“•A hard disk containing the system partition was removed prior to beginning SP1 installation.

“•Windows is running on a storage area network (SAN), and access to the system partition has been disabled.

“•A disk management tool from another software manufacturer was used to copy (or clone) the disk or partition on which you’re trying to install SP1.”

fix for this problem. For example, they can mount the system partition themselves by firing up Command Prompt with administrative rights, and entering the following command: mountvol /E.

Of course, in scenarios in which the HDD with the system partition has been removed, customers will need to return the hardware in order for SP1 RTM to take advantage of the system partition.

Microsoft advices those running Windows from a SAN to visit the SAN manufacturer’s support website, or to ask the company directly for guidance on how to access the system partition.

“If a disk management tool from another software manufacturer was used to copy (sometimes called clone) disks or partitions on your computer, the SP1 installer might not be able to identify the correct system files.

“Turn off your computer and physically disconnect any external disks or drives that aren’t required for starting Windows. Turn on your computer, and then try installing SP1 again,” the company noted.

If you need any help and support please don’t hesitate to contact us

  1. D. Charles Pyle
    February 24, 2011 at 5:23 am

    Sometimes, none of the above solutions from Microsoft work. This is due to a differing configuration, such as in my case. I have a single hard disk wired to the SATA port.

    This single drive is a multiboot configuration with a hybrid GPT/MBR partition system, using a third-party boot manager to boot Windows 7 and a BSD-derived OS. The Windows 7 32-bit partition is on MBR while the BSD-derived OS is installed on the GPT partition. A System Reserved partition was never installed on the hard drive by Windows 7’s installer.

    The problem is that without that System Reserved partition, the Service Pack 1 installer looks to the Active partition for the files it needs to update before proceeding with the remainder of the update to SP1. This is also the case when on a dualboot and multiboot system this System Reserved partition is never installed. In this case all of the boot code and Windows 7 Boot Manager files were installed on the Windows C: drive. The installer of SP1 does not expect this subtle difference since it is not the default.

    How to solve the dilemma if in the same boat as was I?

    Simply log onto Windows 7 as an administrative user, run the Disk Management snap-in within the Computer Management Console and write down the currently active partition, and then mark the Windows 7 partition as active using either DISKPART or the Disk Management snap-in within the Computer Management Console.

    Then, you should be able to install Windows 7 Service Pack 1 without a hitch, if there is no other differing problem to crop up. Allow the installation to finish and allow it to reboot and configure the system.

    After logging back into Windows 7, open a Command Prompt as an administrative user and use DISKPART to set the original active partition back to active and reboot. Everything should be working as originally, only you now will have Service Pack 1 installed.

  2. Rick
    March 11, 2011 at 10:07 am

    In my case, all the req’d Windows partition(s), including the only 100Mb sys part, on “sda” were “active” and looked ok.
    However, I still got the “Windows 7 SP1 Installation Error 0x800F0A12”

    My scenario:
    I simply have mutiple (sata)disks, with each OS purposely installed separately on their respective bootable disks, sda->Win7, sdb->Linux, sdc-> …, … with no raid’s, vm’s, ….
    My 100Mb sys/mbr resrved parttion on “sda” looked fine, however a recent install of Kubuntu onto a separate sata disk “sdg” overwrote my Windows sys/mbr bootloader on sda ? -yep, “overly zealous” grub2 with no options as to which disk/mbr I want it to install to ?

    my solution:
    In windows, as administrator just copy “boot\bootsect.exe” from a Win7-Installation-DVD temporarily over to for example “c:\”, and just run as an administrator in a command prompt:
    bootsect.exe /nt60 SYS /mbr /force
    This fixed/restored my original 100Mb sys.mbr back onto “sda”, and afterwards, I had no problems installing Win7 Service Pack 1, …

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