You cannot download updates when you access the Windows Update Web site from a Windows XP-based computer that is behind a firewall or a proxy server

When you access the Microsoft Windows Update Web site from a Microsoft Windows XP-based computer that is behind a firewall or a proxy server, you cannot download the updates. You may also see one of the following error messages in the upper-right corner of the Web page:Note You can view the Windowsupdate.log file to verify whether Windows Update or whether Automatic Updates encountered an error. By default, the Windowsupdate.log file is configured to log messages. This log file is located in the %Windir% folder. The %Windir% folder is the folder where Windows is installed in your computer.

Windows XP uses Microsoft Windows HTTP Services (WinHTTP) to communicate with the Windows Update Web site. Windows XP also the Background Intelligent Transfer Service (BITS) to download updates. The error messages that are mentioned in the "Symptoms" section indicate the following:

• The client was able to find the proxy or the firewall.
• The client received an error message.
• The client was denied access to the Windows Update site.

To resolve this issue, make sure that the proxy server or the firewall is configured for anonymous access to the Windows Update Web site. Include the following destinations when you create the destination set or the URL set for Windows Update:

• http://download.windowsupdate.com
• https://*.windowsupdate.microsoft.com
• http://*.windowsupdate.microsoft.com
• http://update.microsoft.com
• http://*.windowsupdate.com
• http://download.microsoft.com
• http://windowsupdate.microsoft.com
• http://ntservicepack.microsoft.com
• http://wustat.windows.com
• https://update.microsoft.com

Note See the documentation for your proxy server or your firewall for information about how to configure the proxy server or the firewall for anonymous access.

For more information about how to configure ISA server for anonymous access, click the following article number to view the article in the Microsoft Knowledge Base:

To work around this issue, Administrators can use one of the following methods to install Windows Updates:

• Use Microsoft Software Update Services (SUS) to install updates. For more information about SUS, visit the following Microsoft Web site:
  http://technet.microsoft.com/en-us/wsus/bb466186.aspx (http://technet.microsoft.com/en-us/wsus/bb466186.aspx)
• Use Microsoft Systems Management Server to install updates. For more information about Systems Management Server, visit the following Microsoft Web site:
  http://technet.microsoft.com/en-us/sms/default.aspx (http://technet.microsoft.com/en-us/sms/default.aspx)
• Manually download service packs, security fixes, and feature updates for Windows XP. To do this, visit the following Microsoft Web site:
  http://www.microsoft.com/windowsxp/downloads/updates/default.mspx (http://www.microsoft.com/windowsxp/downloads/updates/default.mspx)

If your proxy server or your firewall is already configured for anonymous access, you can gather more information about the actual cause of the error messages that are mentioned in the "Symptoms" section by using the Network Monitor Capture Utility. You must keep the Network Monitor Capture Utility running when you access the Windows Update Web site for the utility to display the actual cause of the error messages. For more information about the Network Monitor Capture Utility, click the following article number to view the article in the Microsoft Knowledge Base: