Microsoft has released tools to block Internet Explorer 10 from automatically reaching corporate PCs running Windows 7 From Computerworld:

The IE10 Automatic Update Blocker Toolkit is designed for enterprises that want to keep workers on an older edition of IE. Its tools include a script that can be run locally, as well as an administrative template IT administrators can use to widely block IE10 through Group Policy settings.

The tools block automatic upgrading of older editions of Internet Explorer to IE10 on Windows 7 and Windows Server 2008 R2 via the operating systems' built-in Automatic Update service. Companies that rely on WSUS (Windows Server Update Services) or SMS (Systems Management Server) do not need the toolkit; they can manage the deployment of IE10 using those programs.

 Microsoft issues tools to block IE10 upgrades on Windows 7