Jaheckelsafar is wise the answer is still there my friend:
Question #1a: What is AVS?
Question #1b: I downloaded a bunch of AVS plug-ins/presets, but they don't show up in the Winamp plug-ins list!
AVS is a visualisation plug-in that isn't limited to predefined effects: the user can combine the library of built-in effects in endless ways to create so-called presets. There are tons of presets available for download on the web, most of which are a lot better than the default presets (they're a bit outdated).
To view these presets, start AVS like any other plug-in and right-click the display. You can then choose from all the presets installed.
I do not what more I can say. Right click on the AVS box with the swirly images in it and all becomes clear. I pursume by you first post the section that AVS is working. As the FAQ says these are preset pack not seperate plug-ins.
The power of the FAQ! Power