We knew that Windows XP users won't be getting Internet Explorer 9, but it appears that Windows 7 users are out of luck too.How is that possible, you ask? An FAQ for IT pros on Microsoft's site, cited by an Ars Technica story yesterday, states that the installation of the final version of IE9 will require Windows 7 Service Pack 1 (SP1). Microsoft has confirmed that Windows 7 SP1 will not be available until the first half of 2011. Windows Vista users will have to have Vista SP2 in place to install IE9.From the FAQ on Microsoft's Web site:When Microsoft releases Internet Explorer 9, will it require Windows 7 Service Pack 1?Yes. Internet Explorer 9 will require Windows\u00a07 Service Pack 1 (SP1). Therefore, organizations must plan, pilot, and deploy Internet Explorer\u00a09 as part of or after a Windows\u00a07 SP1 deployment.The FAQ did confirm that IT pros will be able to add IE9 to existing Windows 7 images to streamline deployments.This Windows 7 SP1 requirement also puts a recent Microsoft blog post into context. In it, Rich Reynolds, general manager for Windows Commercial, extols Windows 7 momentum, calls out big-win Windows 7 customers such as BMW and Expedia and cites high enterprise adoption numbers from an IDC study.\nSlideshow: Seven New Windows 7 Tablets: In PicturesSlideshow: Windows 7 Hardware in Pictures: The Latest and Greatest Laptops\nSlideshow: Internet Explorer 9: A Visual Tour\nHe also offers guidance for deploying Internet Explorer but does some tap dancing around the subject of IE9 and Windows 7. Reynolds never says explicitly that installation of IE9 will require Windows 7 SP1. Why not just come out and say it? Because it could complicate things and Microsoft needed to finesse its message.And that message is: Embrace IE9 because it's revolutionary but don't worry about it now. Just keep on truckin' with those Windows 7 deployments!If businesses start thinking they have to wait to deploy a service pack just to install a new version of IE or wait for IE9's release to implement Windows 7 at all, they may just find it easier to stay with Windows XP. And a Microsoft customer do nothing is bad for business. It's also a big, intimidating jump for such businesses still languishing on XP and IE6 to leapfrog two OS generations and three browser generations.So the loud and clear message from Microsoft is: deploy Windows 7 right now with IE8 because there's a smooth transition to IE9 waiting for you in 2011. The more understated message: We're on a roll with Windows 7 so please, please don't wait for SP1 to deploy it."Until the final code of Internet Explorer 9 is released to the Web, we recommend businesses first move to Windows 7 Enterprise with Internet Explorer 8 so they can immediately benefit from the enhanced security, manageability, web standardization, and lifecycle support that Internet Explorer 8 brings to enterprise browsing, today," Reynolds writes in the blog post."Your investments in Internet Explorer 8 will put your business on the path to realizing the benefits of Internet Explorer 9 when it becomes commercially available."Microsoft has not given an exact release date for either Windows 7 SP1 or IE9. However, both betas are out there now and the two are on a collision course for final release around the same time in the first half of 2011. It certainly would make sense to have IE9 be included as part of Windows 7 SP1. But it makes even more sense to have IE9 work on the version of Windows 7 that everyone uses now.All of this smacks of poor planning and seems like a recipe for slow IE9 adoption. I mean, if Microsoft releases IE9 before Windows 7 SP1, who will even be able to install it? I guess just Vista SP2 users. Are there any of them left?UPDATE: After this post was published, Microsoft admitted that the requirements for IE9 on its Technet FAQ page were not accurate and that Internet Explorer 9 will indeed work on both Windows 7 RTM and Windows 7 SP1.The guideline has been changed to:When Microsoft releases Internet Explorer 9, will it require Windows 7 Service Pack 1?No. Internet Explorer 9 will install on systems that have either Windows 7 RTM or Windows 7 with Service Pack 1 (SP1) installed. When you install Internet Explorer 9 on a system that has Windows 7 RTM installed, additional operating system components are included as part of the installation of Internet Explorer 9. When you install Internet Explorer 9 on a system that has Windows 7 SP1 installed, these additional components are already present with Windows 7 SP1, and do not need to be reinstalled when you install Internet Explorer 9. For this reason, a system reboot is not required when you install Internet Explorer 9 on a system that has Windows 7 SP1 installed. Shane O'Neill covers Microsoft, Windows, Operating Systems, Productivity Apps and Online Services for CIO.com. Follow Shane on Twitter @smoneill. Follow everything from CIO.com on Twitter @CIOonline. Email Shane at email@example.com.