Installing Windows 7 SP1 on chainloaded Windows

The Problem

When I try to install Windows 7 Service Pack 1 (SP1) on my dual-booting computer, installation fails every time with the error 0x800F0A12.

My Setup

Drive 0

Drive 0 has Windows 7 installed. In the setup wizard, I just deleted all partitions, clicked the blank drive, clicked Next and let Windows handle the partition scheme, boot options, etc. the way it wanted. So there is no GRUB config or code here.

Drive 1

Drive 1 has Ubuntu installed with my preferred partition scheme. GRUB is installed to this drive and there is an entry for Windows 7 on Drive 0.


In BIOS, I boot Drive 1 by default and just select Windows from the GRUB menu when I want to use Windows.

The Cause

If you can believe it, Windows was cranky because I was using GRUB to chainload Windows’ own bootloader!

The Solution

So the solution was to select my boot device at boot time (F12 during POST on my board) and boot from Drive 0 directly. SP1 is now installing without a hitch.


Once the installation is complete, you can continue chainloading Windows’ bootloader with GRUB. It’s only the SP1 installation that gums it up.


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One Response to Installing Windows 7 SP1 on chainloaded Windows

  1. Steven says:

    Windows has always been cranky about that. A big thing is if you ever want to do away with Linux and just run Windows alone you’ve got to make sure every piece of Linux and the grub is gone. Then reinstall Windows and format it all or else. Hard drives become unusable real quick if everything isn’t taken care of.

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