A standalone Windows Installer 4.5 SDK has been released to the Download Center.  This Windows Installer SDK release contains updates to tools, utilities, samples, and documentation for Windows Installer 4.5.  Aaron Stebner blogged about the new and improved features, and an new KB article describes what is included and what got fixed.  These updated Windows Installer files will also be included in the next version of the Windows SDK.

The Windows SDK installed prior versions of the Windows Installer files by default to %ProgramFiles%\Microsoft\Windows SDKs\[version]. This new standalone SDK installs the Windows Installer content to a different default location of %ProgramFiles%\Windows Installer 4.5 SDK, and therefore will not overwrite files installed by the Windows SDK.

Included in the Windows Installer 4.5 SDK:

• Updated versions of a set of these Windows Installer Development Tools, including the popular installer for Orca, installed by default to  %ProgramFiles%\Windows Installer 4.5 SDK\Tools.
• Headers, libraries, patch building samples and sample code for Windows Installer developers.
• Windows Installer help documentation in CHM format installs to %ProgramFiles%\Windows Installer 4.5 SDK\Doc\msi45.chm This CHM file has not shipped with the Windows Installer SDK in a while, and it is a handy reference for Windows Installer-specific information.

The MSDN Windows SDK Developer Center is the place to find resources and links to Windows SDK products, release notes, technical articles, and more.