ITC Processing has been available on ATI graphics cards since Catalyst 9.2 though it can have a positive or negative impact depending on your display device.

Enabling ITC Processing for DTVs

• ITC processing is a feature that enables display processors to use the appropriate pixel data processing algorithms based on specific content type to ensure video quality.
• With ITC processing, the graphics driver enables the display to use its own video quality processing algorithms for movies played in full-screen mode on HDMI™ displays.
• Note: This feature is available only for DTVs connected with HDMI cables and may not be available for all systems.

How to enable this in the ATI Catalyst Control Center

• From the Graphics Settings tree, expand DTV.
• Click Attributes.
• Select or clear Enable ITC Processing as appropriate.
• Select—Enables ITC processing for HDMI displays that are capable of the feature. When movies are played in full-screen mode, the display’s processors can be used to ensure video quality.
• Clear—Disables ITC processing. Video quality is ensured by the graphics driver for all types of contents displayed.

ATI Catalyst™ 9.4 HDMI Audio Driver for Windows XP Professional/Home Edition

The Catalyst™ Software Suite states that the HDMI Audio driver is supported on the Windows Vista OS only at this stage.  Its never straightforward, especially with the HDMI driver hiding on the AMD website.

Here is the Realtek ATI HDMI Driver, this may also help.