Microsoft MSXML

Microsoft XML Core Services (MSXML) is a set of services that allow applications written in JScript, VBScript, and Microsoft development tools to build Windows-native XML-based applications. Different versions of MSXML are included with various Microsoft products, such as Microsoft Windows, Microsoft Internet Explorer, Microsoft Office, and Microsoft SQL Server.

Current Versions: (source: http://en.wikipedia.org/wiki/MSXML)

MSXML 6.0

MSXML6 is the latest MSXML product from Microsoft, and (along with MSXML3) is shipped with Microsoft SQL Server 2005, Visual Studio 2005, .NET Framework 3.0, Windows Vista, Windows 7 and Windows XP Service Pack 3. It also has support for native 64-bit environments. It is an upgrade but not replacement for versions 3 and 4 as they still provide legacy features not supported in version 6. Version 6, 4, and 3 may all be installed and running concurrently. MSXML 6 is not supported on Windows 9x. Windows XP SP3 includes MSXML 6.0 SP2.

MSXML 5.0

MSXML5 is a binary developed specifically for Microsoft Office. It originally shipped with Office 2003 and also ships with Office 2007. Microsoft has not released documentation for this version because Microsoft considers MSXML 5 an internal/integrated component of Office 2003. MSXML 5 is not included in Office 2010.

MSXML 4.0

MSXML4 was shipped as an independent, downloadable SDK targeted at Independent Software Vendors and third parties. It is an upgrade for, but not a replacement to MSXML3 as version 3 still provides legacy features. There is no 64-bit version offered, although the 32-bit version is supported for 32-bit processes on 64-bit operating systems. Versions 4 and 3 may be run concurrently. MSXML 4.0 SP3 is the most recent version released in March 2009, SP2 support expired in April 2010.

MSXML 3.0

MSXML3 is a current MSXML product, represented by msxml3.dll. MSXML 3.0 SP2 first shipped with Windows XP, Internet Explorer 6.0 and MDAC 2.7. Windows XP SP2 includes MSXML 3.0 SP5 as part of MDAC 2.81. Windows 2000 SP4 also ships with MSXML 3.0. By default, Internet Explorer version 6.0, 7.0 and 8.0 use MSXML 3 to parse XML documents loaded in a window. MSXML 3.0 SP7 is the last supported version for Windows 95. Windows XP SP3 includes MSXML 3.0 SP9. Windows Vista also includes MSXML 3.0 (SP10).

Here you can find the complete version-list: http://support.microsoft.com/kb/269238