Windows 7 users won't be able to install Internet Explorer 9 until they have also installed the as-yet unreleased Service Pack 1 (SP1) for the operating system, according to Microsoft.
We already knew that IE9 wouldn't be available for Windows XP and that Vista users would need to install the Service Pack.
However, the news that the very latest version of Windows would need an upgrade comes as a surprise.
"Internet Explorer 9 will require Windows 7 Service Pack 1 (SP1)," Microsoft said in an FAQ on its TechNet website. "Organisations must plan, pilot, and deploy Internet Explorer 9 as part of or after a Windows 7 SP1 deployment."
Microsoft is remaining tight-lipped on final release dates for IE9 and SP1, but both are expected in the first half of next year.
The announcement suggested the two updates may appear simultaneously, but Microsoft not surprisingly given the push to move enterprises from XP - said companies should not wait for SP1 and IE9 before upgrading systems.
"Organisations should not disrupt on-going deployment projects, but continue deploying Windows 7 and Internet Explorer 8," the company said.
"Investments made in this effort will carry forward when they deploy Windows 7 SP1 and Internet Explorer 9 at a later date. With Internet Explorer 8 in place, they will be in a good position to rollout Windows 7 SP1 and Internet Explorer 9 with minimal effort."
Microsoft had previously said the SP1 update would not include new features, only security patches and fixes.
Anyone wanting to run the beta of IE9 on Windows 7 machines need to install four updates, all available via Windows Update: KB2028551, KB2028560, KB2120976 and KB2259539.
