Error message when you try to use the Windows Update or Microsoft Update Web sites to install updates: "0x800B0100"

When you try to install updates from the Windows Update Web site or from the Microsoft Update Web site, you may receive the following error message:

This issue occurs if Windows security .dll files are registered incorrectly.

To resolve this issue, use the following methods according to the specific Microsoft Windows operating system that you use.

Method for Windows 2000, Windows XP, or Windows Server 2003

To resolve this issue, register the Softpub.dll, Wintrust.dll, Initpki.dll, and Mssip32.dll files. To register these files, follow these steps:

1. Click Start, click Run, type cmd, and then click OK.
2. At the command prompt, type regsvr32 Softpub.dll /s, and then press ENTER.
3. At the command prompt, type regsvr32 Wintrust.dll /s, and then press ENTER.
4. At the command prompt, type regsvr32 Initpki.dll /s, and then press ENTER.
5. At the command prompt, type regsvr32 Mssip32.dll /s, and then press ENTER.

Method for Windows Vista or Windows Server 2008

To resolve this issue, run the System Update Readiness Tool (Checksur.exe). To do this, follow these steps:

1. Download and run the System Update Readiness Tool. This tool runs a one-time scan for inconsistencies that may prevent future servicing operations. For more information about how to download and run the Checksur.exe tool, click the following article number to view the article in the Microsoft Knowledge Base:
   947821  (http://support.microsoft.com/kb/947821/ ) Description of the System Update Readiness Tool for Windows Vista
2. Try to install updates again.

Note After you run the tool, the Checksur.log file is located in the following location: In a default installation of Windows Vista, this file is in the following folder: