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Code 800F0900. Windows update encountered an unknown error


New member
Nov 1, 2014
Hope you can help.... I have the above error on windows update. It is on a Win 7 HP 64 bit machine. Strangely Windows update says that the most recent check for updates was on 27/08/2014 but that updates were installed on 04/10/2014 :confused2:

I have run Windows update troubleshooter and it fixed Service Registration is missing or corrupt but failed to fix problems installing recent updates

As requested I have also run SFC Fix and got the following report:
SFCFix version by niemiro.
Start time: 2014-11-02 09:56:32.879
Not using a script file.

SUMMARY: Some corruptions could not be fixed automatically. Seek advice from helper or sysnative.com.
CBS & SFC total detected corruption count: 0
CBS & SFC total unimportant corruption count: 0
CBS & SFC total fixed corruption count: 0
SURT total detected corruption count: 1
SURT total unimportant corruption count: 0
SURT total fixed corruption count: 0
AutoAnalysis:: directive completed successfully.

Successfully processed all directives.
SFCFix version by niemiro has completed.
Currently storing 0 datablocks.
Finish time: 2014-11-02 09:56:54.669

I have also attached the CBS folder as requested. There is one file i can't attach as even when zipped it is 11.3Mb! It is titled CbsPersist_20140821192720.cabView attachment 9698View attachment 9699View attachment 9700View attachment 9701

Can anyone help sorting this out. I hope I've given you the right info..if not apologies, let me know what you need.

Thanks in advance....

Go The Power

Senior Administrator, Windows Update Expert, Contributor
Mar 5, 2012
Adelaide, South Australia
Hello and welcome to the forum.

There is a corrupt Windows Update Agent file that appears to be causing this issue.

SURT Package replacement

Warning: this fix is specific to the user in this thread. No one else should follow these instructions as it may cause more harm than good. If you are after assistance, please start a thread of your own.

  1. Click Here to download Packs.zip and save this to your Desktop.
  2. Right-click on the file and select Extract All...
  3. Tick the box labelled Show extracted files when complete then click Extract
  4. A window will open showing two folders, Manifests and Packages
  5. Open the Manifests folder and copy the files into the following folder (if there are any files)

  6. Open the Packages folder and copy the files into the following folder (if there are any files)

  7. Run the System Update Readiness Tool (SURT) again.
  8. When the SURT finishes installing, copy (Ctrl + C) and paste (Ctrl + V) the contents of the SURT log into your next post please: