Microsoft KB Archive/174591

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Article ID: 174591

Article Last Modified on 11/1/2006


  • Microsoft Internet Explorer 1.0
  • Microsoft Internet Explorer 2.0
  • Microsoft Internet Explorer 3.0
  • Microsoft Internet Explorer 3.01
  • Microsoft Internet Explorer 3.02
  • Microsoft Internet Explorer 4.0 128-Bit Edition
  • Microsoft Internet Explorer 4.01 128-Bit Edition
  • Microsoft Internet Explorer 5.0
  • Microsoft Internet Explorer 5.01
  • Microsoft Internet Explorer 5.5
  • Microsoft Internet Explorer 3.2
  • Microsoft Internet Explorer 4.0 128-Bit Edition

This article was previously published under Q174591


When you install Internet Explorer, the System.1st file in the root folder of the boot drive may not be updated.


This behavior can occur in either of the following situations:

  • The original System.1st file is not present during the installation of Internet Explorer.
  • Your computer is low on disk space. The creation of the new System.1st file is skipped to ensure the successful installation of Internet Explorer.


To resolve this issue, copy the System.dat file to the System.1st file. To do so, follow these steps:

  1. Click Start, point to programs, and then click MS-DOS Prompt.
  2. Change to the Windows folder by typing the following line and then pressing ENTER


    where <windir> is the folder in which Windows is installed.

  3. Type the following lines, pressing ENTER after each line:

          attrib -s -h -r system.dat
          attrib -s -h -r c:\system.1st
          copy system.dat c:\system.1st

    NOTE: If you are prompted to overwrite a file, choose Yes.

  4. Type exit, and then press ENTER.
  5. Shut down and restart your computer.


The System.1st file is not used in normal Windows usage. It is intended for use by support professionals as a known good registry file. There is no problem running Internet Explorer with an outdated System.1st file or no System.1st file.

To verify that the System.1st file was updated with Internet Explorer settings before using it to replace the registry, check the "Integrated Browser.ini" file. If the System.1st file was updated, it is listed in this file (usually the second entry).

If the Windows Desktop Update component is installed, the registry is backed up. The old desktop files are backed up to the "Integrated Browser.dat" file and the corresponding "Integrated Browser.ini" file is created. Additionally, the original System.1st file is also backed up and stored in the "Integrated Browser.dat" file. A command that copies the System.dat file to the System.1st file is added to the RunOnce key in the registry. The System.dat file is copied to the System.1st file the next time the computer is restarted or the RunOnce key is processed. The validity of the System.1st file is not checked.

For additional information about how to determine which folder Windows is installed in, click the article number below to view the article in the Microsoft Knowledge Base:

305792 How to Determine Which Folder Windows Is Installed In

Additional query words: 4.00

Keywords: kbenv kbsetup KB174591