Error: We couldn’t complete the updates, Undoing changes. Don’t turn off your computer.

After a month, countless wasted hours and untold frustration trying to install 2919355 it is clear to me that Microsoft does not care and/or does not have a clue as to how to rectify this situation THEY have created.

I have an Acronis backup of my system before this wretched update was attempted. (I didn't like the look of the size of it ). If I restore this backup has anything changed that will make the update now have a reasonable chance of success or is it still the same piece of rubbish that was originally released.

@ConanDestroyer, I am in the same boat.  I have an Acronis backup of my C: partition from April 9th that I may try to restore (most of my user data is on another partition).  However, if the problem is with the System Recovery Partition, then that will not help.  A few of the things I hope Level 2 can resolve tomorrow include: which of the three partitions at the front of the drive are being changed by KB2919355 and were any of them changed by the Win 8.1 upgrade (I regularly backup the EFI System Partition but not the Recovery Partition).

Do you happen to have a spare harddrive available that you could restore your backup to and test, rather than overwriting your existing harddrive?  I reclaim working harddrives off laptops that have been replaced.  Buying a new harddrive might be a worthwhile investment (cost vs. your time).

You must be a mind reader. I've just installed another drive and got it working, the old system disk was dual boot and the MBR needed tweaking, don't know why. I don't have any recovery partitions. I don't trust Msoft to look after my backups - hence the Acronis backups. I've made the W8 system disk much bigger on the new drive so my new strategy is try fixing a system where the update was not successful and if that fails try the backup prior to the update. Fortunately, being retired, time is not a problem.

Thanks for the interest.

My error codes in trying latest Windows updates since 15th May 2014:

80070002 (7 times)

80246013 (1 time)

80070001 (2 times)

80246007 (1 time)

That pretty much matches the codes that I see, with 80246007 showing the most.

In the update history, it actually shows that 355 was installed successfully in some instances, in one case it showed a fail and a success just two lines apart.

And even thought he latest try shows it was installed successfully, something obviously was not as it keeps pestering me to install the latest updates. It then goes through the same routine as others have described, eventually reaching the "undoing changes" part.

Just got this from the mod

What is the date of your backup?

That is important because the Update package has been modified at least once since it's original release on April 8.

If your backup is Apr 8 or before, you do have a greater chance of success.

If you choose to restore to your backup, I would suggest you try this before attempting the update.

From an Administrator Command Prompt window run these DISM commands

• DISM.exe /Online /Cleanup-image /Scanhealth
• DISM.exe /Online /Cleanup-image /Restorehealth

Reboot

If one of the commands fails, that would demonstrate a problem existed before the Update.

If the commands show success, your machine should be ready to apply the update.

I would recommend the manual method of obtaining the package from the Download Center and installing it that way.

Looking at the dates you must be the unluckiest person in the world