When trying to install Windows security rollup update on computer with dual boot, Windows Update always fails.

Symptom

During shutdown, Windows starts preparing the update and during the next boot, it continues until around 80-100%. Then it fails, rolls back the upgrade and reboots again. After that, the update is still listed for installation and shows as failed attempt in the update log with error code 80004005.

Solution

1. Get Windows to boot using its native boot loader

Windows will then boot the active partition from MBR, temporarily remove the boot loader!. So make sure that partition where Windows is installed is the active partition (e.g. using Disk Management)!

Start Ubuntu (either installed one or from a USB Stick) and run following commands:

sudo apt-get install mbr
sudo install-mbr -i n -p D -t 0 /dev/sdX

(replace sdX with the disk where Windows is installed!)

Attention: This makes your linux installation unbootable if you run mbr command on the disk you normally boot Linux from, so ensure:
- you have a current backup of your value data
- have a USB stick at hand with Ubuntu ISO Image

If you have installed Windows on an other (second) harddisk, also go to BIOS Setup and change boot order so the disk containing Windows is in first order (before the one containing Linux).

2. Install Security Rollup Update

On subsequent reboots, your computer will now boot directly into Windows (without showing GRUB menu anymore).

Start Security Rollup Update again:
* Go to Windows Update (Control Panel -> Sytem and Security -> Windows Update)
* Choose "Check for updates"
* Make sure Security Rollup is selected
* Choose "Install Updates"

This time, after 2-3 reboots, update should succeed.

3. Make Linux bootable again

a) When changed boot order to start Windows directly from another disk, go to BIOS Setup again and switch order back, so the harddisk with GRUB installed will be ordered before the HD containing Windows installation.

b) When installed "original" MBR to the disk where GRUB was installed, you have to repair the Linux Bootloader:
* boot using a USB Stick containing e.g. Ubuntu Linux ISO image
* mount your root and boot Linux partitions, e.g.

mkdir -p /mnt/root && mount /dev/sda6 /mnt/root && mount /dev/sda5 /mnt/root/boot

(replace with device where your linux partitions resides, if in doubt, first run fdisk -l /dev/sda)

* chroot your Linux installation:

chroot /mnt/root /bin/bash

* install grub again to Master Boot Record, e.g.

grub-install /dev/sda

(grub configuration should be available on /boot)

* Exit chroot environment

exit

* Unmount Linux partitions:

umount /mnt/root/boot /mnt/root

* reboot your system

You now should see GRUB boot menu again, where you can boot either Linux or Windows...