Software update: DirectX 8.1b

The-Force indicates that a new DirectX version has been released for Windows 2000 and Windows XP. You can also install this version on Windows XP, but you must also have the latest Service Pack installed.
Unfortunately, there is no changelog for this new version, but Microsoft does write the following:

Microsoft DirectX® 8.1b is the latest version of DirectX technology, which delivers fast performance for DirectX-enabled games and other rich media software. This version of DirectX can replace the all previous released versions of DirectX. It includes several critical fixes for Direct3D® and DirectShow® components.

Download:
DirectX 8.1b English