Ok, this happens to people somewhat infrequently but when it does its painful. You get your system all cleaned up and remove all the Windows virus's and Windows Spyware and everything works great.

You go to do the windows updates and it fails with this error message.
Error number: 0x80072EFD

here is one way you can resolve this problem.

SYMPTOMS
Windows XP users may experience issues while connecting/downloading the Windows update.

CAUSE
This issue can be due to corrupted/incorrect version of IUCTL.dll file.

RESOLUTION
To resolve the issue with Windows update, perform the following: Open C:WUTEMP folder and delete the contents of the folder (If any files exist).

Go to "WindowsUpdate" folder in "Program Files" folder, and delete all the contents except the "V4" folder.

NOTE: "WindowsUpdate" is a hidden folder. Highlight the "V4" folder, then click Edit from the menu bar at top of the window and choose Invert Selection.

If you cannot locate the "V4" folder, please skip this step, and then continue to delete the rest of the files by choosing Select All instead of Invert Selection.

If you see the V4 folder, open it and delete all the contents of it except the "iuhist.xml" file.

Also, delete all the contents of the C:WUTemp folder.

Once after deleting all the files, you need to unregister the old control. Follow the below mentioned steps:

Click Start, Run.
Type: "regsvr32 /u C:WINNTSystem32IUCTL.dll" (Without Quotes. You should get an unregistered successfully message.)

Find the old site controls and delete the same. Ensure that you don't have "IUCTL.DLL" and "IUEngine.dll" files located in the system.

Restart Windows and try accessing Windows update.
If the issue still persists, you can download the iuctl.cab file and update the existing files. Proceed with the solution recommended in the following knowledge base article:

http://support.microsoft.com/?kbid=836986
Save iuctl.cab, and extract its contents into a folder. You will get the copy of iuctl.dll, iuengine.dll, and iuctl.inf files.

Right-click on iuctl.inf and select install. This will install the new iuctl.dll and iuengine.dll.

Open Internet Explorer, clear out temporary internet files, and access Windows update.
APPLIES TO
• Microsoft Windows XP Home Edition
• Microsoft Windows XP Professional
• Microsoft Windows XP Media Center Edition 2002
• Microsoft Windows XP Tablet PC Edition

Keywords:
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The original article on this can be found at Microsofts support site