This program is a Winamp 2.x/5.x input plugin to play .ac3 and .dts files. Based on the same decoder library used in AC3Filter.
Just download the latest version and run the installer. After this Winamp will be able to open and play AC3 and DTS files in any stereo, multi-channel of SPDIF mode.
You can see the activity of currently playing audio and change plugin settings. To do this press Ctrl-P in Winamp and go to Plug-ins -> Input -> WinampAC3 (double click on it or press 'Configure' button):
After this you will see WinampAC3 configuration:
Also, to avoid the long path to this window you can enable the tray icon at System page. So when WinampAC3 is active you will see tray icon and can access WinampAC3 by double-clicking it.
Most of the settings in WinampAC3 are common with AC3Filter, therefore to get more help on it, see AC3Filter Help.