TL;DR version at the bottom
I've been trying to update my Vaio Netbook from Windows 7 to 10, unfortunately with no luck up until now. I will explain in a few steps and hopefully someone else will find this useful as well:
First of all my setup. A bit complex, as I have a quad boot of the following partitions on my Setup
Primary #1 Windows 7 Recovery
Primary #2 Windows 7 (original OS that came with the laptop)
Primary #3 Windows 8 (installed after windows 7)
Extended #4 Several Logical Partitions with two Linux installations
So, currently I have the following bootloaders: GRUB (linux bootloader), Windows 7 Bootloader, Windows 8 Bootloader.
I decided a few days ago that I no longer wanted 7 & 8, and that I would nuke the Windows 8 and upgrade my Windows 7 to 10 all the way. I went ahead and simply formated the Windows 8 partition (played around and reallocated space / extended other partitions), refreshed my GRUB bootloader's entries and noticed that Windows 8 Bootloader was still there. I tried to boot into it, and it simply started loading a Windows 8 Recovery so I just rebooted the system - thinking that the Windows 8 bootloader was just left over and was useless.
I then downloaded the Windows 10 media creation tool, tried to update the system but it rebooted with an error. Can't recall what the error was, but I wasn't too mad since I knew my installation was a bit complex. I then went on trying to install Windows 10 about 7 more times, failing each time after the initial reboot with the following error:
with an error code of:
The installation failed in the SAFE_OS phase with an error during BOOT operation
Every single time, no matter whether I chose to keep nothing, everything, tried updating Windows 7 first (which ended up breaking my Windows Update, and then breaking my Network Drivers), tried removing several devices as suggested in a lot of posts with the same error code in Windows7/8/10 forums, all resulting in the same error.
I then remembered that I still have two Bootloaders for Windows, and I figured that the installer probably fails because each time the machine reboots I choose to launch the Windows 7 bootloader, which is probably used as a hack by the devs to tell that something went wrong. So, this time after running the windows upgrade and the machine automatically reboots, I choose the Windows 8 bootloader and all of a sudden the Windows 10 installation continues on my Windows 7 OS.
And here I am, after 2 days of reading relatively unrelated threads, thinking whether it was my fault or not. Surely, my setup was complex, but this simply means that if someone (for whatever reason) needs to have Windows 7 and Windows 8, and then chooses to upgrade Windows 7 to 10, things are gonna get messed up.
I understand that I am probably the only person to ever fall into this bug, but this also suggests that Windows Bootloaders might be a bit hard-coded, and don't keep in mind that other OS's might rely on the same setup - which shouldn't be the case when a Windows Upgrade is as strongly pushed as Windows 10 was. I am sure there are great reasons as to why Windows Bootloaders prefer to ignore everything the machine has to say about itself and do their own thing, but then we have bugs like this one.
I'm not really sure if developers read these forums, but if they do I'd like to hear a technical explanation of my bug.
TL;DR: Had Win7 & Win8 (installed after), tried to upgrade Win7 to Win10 and fell to the same ambiguous error over and over until I continued the installation through Win8 bootloader as a shot in the dark. Suggests possible bug in Windows bootloaders.
My only suggestion to other people who reach this thread by googling for the errors I posted is:
If you've ever installed multiple Windows instances on the same hard drive, the Bootloaders are probably kept and are causing you this issue.