Andreas Demmer

Yesterday, I wanted to install the recently released Service Pack 1 for Windows 7, because I run a Windows 7 in parallel to me beloved Linux, because I need it from times to times for my job. Unfortunally the installation failed shortly after the start dialogue with an unknown error message (error 0x800F0A12). This article tells you, how to fix it.

After some research, I identified the bootmanager Grub to cause this trouble: Windows 7 SP1 refuses to install on dual boot installations if another bootmanager is present. The solution was to remove Grub first, restore the Windows bootmanager, boot Windows, update it to SP1 and restore Grub afterwards.

This is what you need:

• a Linux live-CD (e.g. KDE Four Live)
• Windows 7 DVD

Now the single steps in detail as follows:

1. Remove Grub

1. Boot the Linux live-CD to the command line and log in as root
2. Start the disk partition tool fsdisk with the path to the harddrive device file, e.g.: fdisk /dev/sda
3. Show the partition table: p
4. Remember the partition number of the Linux partition marked as bootable and the Windows partition marked as non-bootable. Mind that partition numbers start counting from 0!
5. Mark the Linux partition as “non-bootable”, e.g. assumed that it is the second partition: a [ENTER] 1 [ENTER]
6. Mark the Windows partition as “bootable”, e.g. assumed that it is the firstpartition: a [ENTER] 0 [ENTER]
7. Show the partition table to verify the result: p
8. Save changes: w
9. Quit fdisk: q

After these steps you need to reboot, whereafter the Windows boot manager should show up instead of Grub. It may most probably complain about the Windows installation beeing broken. This can be fixed as follows:

2. Restore Windows boot manager

1. boot Windows 7 DVD
2. confirm language settings
3. Choose the rescue option in the following dialogue, then select your Windows installation and choose the extended Settings (no (!) complete automated recovery)
4. let Windows setup check and repair your start options or alternatively run on the rescue console: bootsect /nt60 ALL /mbr

3. Install Service Pack

After a reboot, Windows should start as usual. Now you can proceed installing the Service Pack. This can be done either by running Windows update or by downloading the according 32bit or 64bit package from Microsoft. Either way, the update should finish successfully now.

Afterwards, we need to restore Grub.

4. Restore Grub

1. Boot the Linux live-CD to the command line and log in as root
2. Start the disk partition tool fsdisk with the path to the harddrive device file, e.g.: fdisk /dev/sda
3. Show the partition table: p
4. Remember the partition number of the Linux partition marked as non-bootable and the Windows partition marked as bootable. Mind that partition numbers start counting from 0!
5. Mark the Linux partition as “bootable”, e.g. assumed that it is the second partition: a [ENTER] 1 [ENTER]
6. Mark the Windows partition as “non-bootable”, e.g. assumed that it is the firstpartition: a [ENTER] 0 [ENTER]
7. Show the partition table to verify the result: p
8. Save changes: w
9. Quit fdisk: q
10. Run the Grub editor: grub
11. Let Grub find the identifier for the Linux partition: find /boot/grub/stage1
12. Grub should now print sth. like “hd0,1″, remind this
13. Tell Grub the install location according to the identifier printed in the previous step, e.g.: root (hd0,1)
14. Install Grub: setup (hd0)
15. Quit Grub: quit

Finished! After a reboot, the Grub bootloader should appear as usual, in which – assumed that you had this configured before going through all of the steps listed on this page – you can switch between your Linux and your Windows installation.

This entry was posted on Thursday, February 24th, 2011 and is filed under HowTos, Linux. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response or Trackback from your own site.

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