Universal Audio Architecture
Universal Audio Architecture, or UAA, was born out of the need to enable consist audio support on the Microsoft Windows platform. Windows did not provide a standard architecture for Audio hardware that could help communication between the operating system and the hardware, so that the operating system user could manipulate its capabilities.
Makers of audio devices (sound cards etc), such as Creative and Realtek, had to include their own user interface for Windows users to be able to control the capabilities of their audio hardware. Each manufacturer used their own interface and so there was no standard to go on for end users.
A side-effect of this necessity was kernel-mode drivers (which were required for the users actions to reach the hardware) that had major development flaws, leading to instability problems within Windows operating systems, particularly with game titles that required the use of audio hardware.
So in 2002, Microsoft unveiled the Universal Audio Architecture (UAA), which had a goal of standardizing the hardware and driver architecture for audio devices in Windows operating systems. By default, Intel High Definition Audio devices are supported (which adds support for PCI and PCI Express hardware), Universal Serial Bus (USB) devices and Firewire devices.
UAA first showed up as an update to Windows 2000 SP4 and Windows XP SP1. Initially you could only get the update from Microsoft Support but the UAA driver is included with Windows XP SP3 and is nowadays provided with almost all audio hardware drivers given by manufacturers. In order for computer hardware to be certified for the Windows Vista operating system, it must comply with UAA - that is it must function without the need for additional drivers.