Microsoft KB Archive/189306

= How the Windows Update Tool Determines if an Update Is Valid =

PSS ID Number: 189306

Article Last Modified on 2/12/1999

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The information in this article applies to:


 * Microsoft Windows 98

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This article was previously published under Q189306



SUMMARY
The Windows Update tool is an online extension of Windows 98. The Windows Update tool downloads software using the following methods:


 * The Product Updates catalog
 * The Windows Update wizard

This article describes how you can use the Windows Update tool to download updated product features, device drivers, and system files, and how the Windows Update tool determines what updates are appropriate for your computer.



The Product Updates Catalog
The Product Updates catalog is an Internet-based service that you can use to update or install product features. Previously installed updates are not listed by default. However, the entire catalog can be displayed.

The Product Updates catalog relies on the Windows Update Active Setup Control to display available software updates. The control determines if updates are applicable by referencing the registry. You can click Show All to display all available updates.

To view the Products Update catalog, follow these steps:


 * 1) Click Start, and then click Windows Update.
 * 2) On the Microsoft Windows Update Web site, click Product Updates.

The Windows Update Wizard
The Windows Update wizard is an Internet-based service that you can use to update Windows 98 hardware device drivers and system files. The Windows Update wizard compares the current hardware device drivers and system files with a back-end database, and then offers to install pertinent updates. Only applicable updates are listed with a corresponding description.

NOTE: There is no means for listing all updates available on Windows Update wizard.

The Windows Update wizard scans the computer for device driver updates, system file updates, and new files. In addition, Microsoft Windows Update is offered as a source for drivers in the Update Device Driver wizard.

To check for device driver updates using the Windows Update wizard, follow these steps:


 * 1) Click Start, and then click Windows Update.
 * 2) On the Microsoft Windows Update Web site, click Product Updates, click Device Drivers, and then follow the instructions on your screen.

Device Driver Updates
The Windows Update wizard can be used to determine if updated device drivers are available. The following steps describe how the Windows Update wizard determines if updated device drivers are available:


 * 1) The Windows Update wizard updates the Hwinfo.dat file on the local computer.

NOTE: The Hwinfo.dat file is a record of the current state of the computer's hardware configuration, as well as a history of previous device drivers and system resources. The Hwinfo.dat file is created during Windows 98 Setup. The file is updated when the Microsoft System Information tool or the Windows Report Tool is run, and when the Windows Update wizard scans the computer. You can use the Microsoft System Information tool to open and view a Hwinfo.dat file.
 * 1) The Windows Update wizard queries the Hwinfo.dat file for a list of Plug and Play identification (ID) numbers. The ID numbers are compared to the database of available packages on the server.
 * 2) If a Plug and play ID number matches, the package is compared to the existing file. The election is based on either version information or the file date depending on the method specified for the package.

System File Updates
The Windows Update wizard may be used to install updated system files. It determines if updates are available using the following steps:


 * 1) The Windows Update wizard scans specific folders and builds a list of file names.
 * 2) Each file package uses one key file to determine if an update is available on the server. If there are any matches based on the file name, the date of the file determines if the update is valid.
 * 3) Finstall.exe is used to install the file(s).

Installing New Files
The Windows Update wizard can be used to install new files to the computer. To install new files, the Windows Update wizard uses the following steps:


 * 1) The Windows Update wizard scans the computer for the presence of specific key files associated with packages that install new files instead of updating existing files.
 * 2) Finstall.exe is used to install the file(s).

Update Device Driver Wizard
The Windows Update tool is available as a source for drivers in the Update Device Driver wizard. To start the Update Device Driver wizard, follow these steps:


 * 1) Click Start, point to Settings, click Control Panel, and then click System.
 * 2) Click the Device Manager tab.
 * 3) Click a device branch to expand it.
 * 4) Click a device, and then click Properties.
 * 5) Click the Driver tab, click Update Driver, and then follow the instructions on your screen.

When you use the Update Device Driver wizard, the availability of an updated driver for a device is determined using the following steps:


 * 1) Device Manager connects to the Windows Update wizard Web site.
 * 2) The unsigned Direct.b1 file is downloaded to serve as the engine for the process. It is used for the duration of this session and then discarded.

NOTE: The Direct.b1 file determines if there is an applicable update for the specified Plug and Play ID on the server. It may download files to the computer without acknowledgement, so it does not meet the requirements of a signed ActiveX control.
 * 1) For security, a signed file containing a text file, the Ident.cab cabinet file, is downloaded to ensure the server name it contains matches the name of the server from which it was downloaded.
 * 2) The device's Plug and Play ID is passed to the Cdm.dll file, which compares it to the list of available packages on the server. If a match is found, the Windows Update wizard downloads the package to the computer and decompresses it.
 * 3) Once downloaded, the path to the files is reported to Device Manager. It is Device Manager that validates the version information and determines if the driver is appropriate.

NOTE: If the Microsoft Windows Update tool is unavailable, you may not have run the Internet Connection wizard. To run the Internet Connection wizard, click Start, point to Programs, point to Internet Explorer, click Connection Wizard, and then follow the instructions on your screen.

Additional query words: icw

Keywords: kbinfo KB189306

Technology: kbWin98 kbWin98search

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