Information
The Windows Rights Management Add-on for Internet Explorer provides a way for users who do not use the 2010 Office release to view, but not alter, files with restricted permissions. By default, IRM-enabled files are saved in a format that cannot be viewed by using the Windows Rights Management Add-on. If this setting is enabled, an embedded rights-managed HTML version of the content is saved with each IRM-enabled file, which can be viewed in Internet Explorer using the add-on. This configuration increases the size of rights-managed files, in some cases significantly.
Solution
Set the policy value for User Configuration -> Administrative Templates -> Microsoft Office 2010 -> Manage Restricted Permissions 'Allow users with earlier versions of Office to read with browsers' to 'Disabled'.