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.
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.”
Users can try and fix this problem themselves. 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.