I cannot tell you if it is the correct window, only that this is a valid name for a class.
If it doesn't work, you can test other window in the app. Most of the time, the video renderer is not the correct one, try to get its parent
Has anyone got milkdrop to work with winamp? The problem I have is the milkdrop visualization window is a child window of winamp, and I can't figure out how to have XMoveWindow just work on the child window.