Service Pack 1 (SP1) installation error: 0x800F0A12

This may apply to imaged systems:

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.

More...

That is good to know. However, some people seem to have that error.

Here is one. At the moment I think GRUB was my problem.

I have this disk layout:

Code:

Disk 1 (Samsung Spinpoint 1TB):
 C:\ > 250GB NTFS Windows 7 (primary, with Windows 7 installed)
 D:\ > 500GB NTFS Data (primary)
 S:\ > 150GB NTFS Software (primary)
     > 100GB NTFS Legacy (primary, with XP installed, not accessible through W7)

Disk 2 (Samsung Spinpoint 160GB):
     > 100GB EXT4 /home (primary)
     >  50GB EXT4 / (primary, with Linux Mint 10 installed)
     >  10GB SWAP (which should be used by Linux Mint 10)

In addition, while installing Mint I also installed GRUB (on disk 2) which takes care of loading all the three OSes (I set the BIOS to boot from disk 2 instead of disk 1 which was the default) and everything has always worked great.

Yesterday, as I was normally using Windows 7 (so I first booted into GRUB then asked it to load Windows 7) I downloaded Windows 7 SP1 and tried to update.
It refused to install giving me that very same error (0x800f0a12).
I've tried several times to start the installer as administrator manually (which isn't required, as it asks anyway for elevation a little after it has been laubched) and to disconnect any other device that could interfer (like the disk I have on eSATA) to no avail.

To get it installed with no trouble, I had to restart the machine and enter the manual boot selector to make it bypass GRUB and boot directly into Windows 7 (don't ask me how I got to the conclusion GRUB was the problem, probably it was the beer).
By doing that, the SP1 installed flawlessly.

So, although I solved my problem, I'm here to ask if there's someone more educated than me that could explain me why it has failed in a way and has succeeded in another, seeing that I never moved the disk which Windows was installed on and the OS was just the very same.
I suppose (but it's really nothing more than a guess) that the installer didn't like the fact Windows 7 was not on the "main" boot disk, but I'm curious to know what triggered this kind of behaviour.

Thanks in advance to anyone who could answer this.. And of course also the little rep I can give :)

I guess you're talking about the 100MB partition that should have been created at startup?
Well, my "System reserved" partition is the whole 250GB partition which hosts the Windows 7 files (I followed this tutorial, especially method three, to avoid creating a primary partition for those system files as I had already planned to use all the 4 primary partitions with the scheme above).
The only difference I noticed is this: my system boots by default from the second hard disk (which is the one with GRUB), and it's GRUB that allows me to choose if I want to boot Windows 7, Windows XP or Linux.
So, the cases are two:

1) The case in which I start the PC normally:

Code:

After POST, GRUB starts (from Disk 2)
   > GRUB lets me choose which OS to boot (and I choose Windows 7)
      > Windows 7 starts (from Disk 1)
         > Windows 7 SP1 refuses to install with the error code shown above

2) The case in which I choose manually to boot from Disk 1:

Code:

During POST, I launch the boot selection popup
   > I choose to boot directly from Disk 1 (so bypassing GRUB, and Disk 2, completely)
      > Windows 7 starts (from Disk 1)
         > Windows 7 SP1 installs with no problem of any kind

So I came to the conclusion that Windows 7 SP1 doesn't like the way the boot sequence is executed if I boot through an external boot loader such as GRUB.

Now I don't know if

• it's because GRUB is on a different hard disk
• or just because GRUB handles the boot sequence differently from how Windows 7 does.

_ EDIT ___________________________________________________________

Doing some research I found this blog entry:
Windows 7/2008 R2 Service Pack 1 fails with 0x800f0a12 - Ramblings of a Support Engineer - Site Home - TechNet Blogs

I find among the comments some advice about moving the "boot" flag from the GRUB partition to the Windows 7 one (e.g. with gparted).
This could probably be done in the case you have GRUB on the same HD you have Windows 7 on, and may solve the problem.

In my case, having a "boot" flag for any HD (Disk 1 had the "boot" flag set to the Windows 7 partition, Disk 2 had it set to GRUB) the only thing I had to do was instruct the system to boot once off Disk 1 before Disk 2.
But I'm confident that moving the "boot" flag with gparted would solve it also for people that have GRUB and Windows 7 on the same disk. They should just remember to put it back where it belongs once finished installing SP1