In Exchange 2010 and Exchange 2007, Exchange Search uses Windows Search to index messages and supported attachments. Installation of 2007 Office System Converter: Microsoft Filter Pack is a pre-requisite for Exchange 2010 (RTM) setup, and after setup completes you must register the filters with Exchange Search. Register Filter Pack IFilters with Exchange 2010 has more information and a PowerShell script to register the IFilters. The Exchange 2007 version is KB 944516 – How to register Filter Pack IFilters with Exchange Server 2007, and contains a VBScript script, but essentially performs the same procedure.
The just-released Exchange 2010 SP1 requires the new Microsoft Office 2010 Filter Packs. SP1 setup registers the IFilters with Windows Search. You’re no longer required to run a shell or VBS script, or manually create registry entries to register the Office 2010 IFilters.