If you're running Visual Studio 2010 on XP or Vista you may benefit from installing Windows Automation APIs, which can significantly decrease Visual Studio IntelliSense performance if WAAPI 3.0 isn't installed.
This article describes how to install WA API 3.0 update, available as a stand-alone download for 32-bit editions of Windows XP and for Windows Server 2003. WA API is a component of the platform update for Vista and of the platform update for Server 2008. Note if you're running XP SP2 you'll be told the patch isn't applicable, that's because you need to upgrade to XP SP3 first. Windows 7 and Windows Server 2008 R2 ships with with Windows Automation API 3.0, so no upgrade is required.
Download Updates From: KB981741