Managing multiple chat windows
Collapse: To collapse a chat window so just the conversation status bar appears, click the gray space next to your friend's name. Collapsed chat windows offer privacy, without having to leave the conversation.
Stack: If you have multiple chat windows open, Google Talk will stack them in chronological order (the person you start talking with first appears at the top of the stack).
Tear off: You can tear chats off of your stack, starting from the bottom window. Drag and drop chat windows into a new stack if you'd like to re-prioritize your conversations, or you can simply place the windows on another part of your screen.