When you visit Windows Update to download updates to your system, the following message may appear:

Thank you for your interest in obtaining updates from our site.

This website is designed to work with Microsoft Windows operating systems only. To find updates for Microsoft products that are designed for Macintosh operating systems, please visit


This means that your system is sending an incorrect data (about the Operating System) to the Microsoft Windows Update server. Windows Update uses the operating system information that the navigator.userAgent property returns to determine if you are running a supported operating system.

To test the User Agent string, open Internet Explorer and type the following:


You'll see the Version, Platform information reported. The same data is reported to a Web server when you visit a website.

This problem may also occur if you access the Internet through a firewall or proxy that does not allow the Windows Update Web site to receive the correct HTTP user-agent request header ("HTTP_USER_AGENT") for Internet Explorer. Some firewalls or proxy servers may send user-agent information that is incorrect or difficult to nterpret.


Open Regedit.exe and navigate to the following locations:

HKEY_LOCAL_MACHINE \ SOFTWARE \ Microsoft \ Windows \ CurrentVersion \ Internet Settings \ 5.0 \ User Agent


HKEY_CURRENT_USER \ SOFTWARE \ Microsoft \ Windows \ CurrentVersion \ Internet Settings \ 5.0 \ User Agent

Backup the keys to separate REG files. See this page for more information.

Delete the User Agent key in the above two locations (if present)

By doing this, any overridden User Agent strings and tokens are removed, and the correct data is reported to a Web server.

Close Regedit.exe and restart Windows.