OK, I now have the TV showing the *desktop*. This is using the S-Video to the S-Video-to-SCART adapter (the thing Webmattijs pictures). But it's not showing the film on the TV screen.
Another source tells me that his iBook sets the screen resolution automatically to "TV" when he plugs it into a TV. My System Prefs don't offer "TV". He also said to look for Dual Monitors in the System Prefs; I can't find any such preference. (He said that when he does this, if he opens DVD Player, its screen on the computer screen is blank, but the film plays on fullscreen on the TV.)
While the TV shows my desktop, it doesn't show what's *on* the desktop; that is to say, sometimes it does and sometimes it doesn't - usually it shows just the desktop, with the apple menu at top, but it doesn't show the Macintosh HD icon, or any windows I have open, including those of programs I might be running (such as DVD Player).