Why won't Internet Explorer 10 run on Windows Vista?

Why does the platform preview of Internet Explorer 10 refuse to install on Windows Vista? Maybe it's because Vista's short, unhappy life will end in less than one year. I help decode the cryptic support lifecycle.
Written by Ed Bott, Senior Contributing Editor

It might seem impossible to believe, but Windows Vista is drawing to the end of its short, unhappy life. Under Microsoft's official product lifecycle, the mainstream support phase for Windows Vista will end in less than one year, on April 10, 2012—five years, two months, and 16 days after it became generally available on January 25, 2007. (For business editions, there's an extended support period that lasts another five years, guaranteeing security updates until 2017.)

I don't expect there to be any great outcry when Vista fades away. But knowing that end-of-life date helps answer one mystery that puzzled some Microsoft watchers this week. Why does the platform preview of Internet Explorer 10 throw up an error message if you try to run it on Windows Vista? Maybe it's because, if the newly announced browser follows the same development schedule as IE9, its scheduled ship date will be a year from now—after Windows Vista is retired.

Decoding Microsoft's cryptic product support lifecycle isn't easy. Even experienced Microsoft watchers sometimes get tripped up by the many conditions that apply. Service packs and browsers complicate the issue even more. Shortly after Windows 7 shipped, I wrote How long will Microsoft support XP, Vista, and Windows 7? and assembled those dates into a table, which is still accurate.

Will the release of a new version of Internet Explorer change those plans? Nope. Here's why.

As the Microsoft Support Lifecycle blog helpfully explained in a 2009 post, Internet Explorer is a “component.” That distinction is important in terms of support dates:

Under the Support Lifecycle policy, we support components with the product or service pack that it shipped for. … Internet Explorer is considered as a component of the operating system (OS) for which it was released. The support timelines for IE are inherited from the OS and its associated service packs. Basically, this means that the versions of Internet Explorer that shipped for a specific OS or service pack will be supported with the support lifecycle of the OS or service pack.


As per the policy, we will not end support [for] previous versions of Internet Explorer on supported operating system versions.

When Windows Vista shifts into its extended support phase next year, that also means the end of the line for any version of Internet Explorer that was released for it. Because the extended support phase lasts another five years, you don't have to worry about security updates for Windows Vista and its supported browsers—even Internet Explorer 7. But you won't get anything new.

It's possible, of course, that Microsoft will allow the final version of IE 10 to install on Windows Vista. But it's also reasonable for them to push web developers to test its platform previews on the latest and greatest Windows, which will be around until January, 2015.

I'm assuming (reasonably, I think) that Windows 8 will still be several months away from its official release when April 2012 rolls around, If that's true, it means that Microsoft will, at least briefly, have only one version of Windows that it's actively supporting.

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