There is no good answer for your question. PowerPoint doesn't do this natively,
so you have to resort to outside software and hardware. Depending on the
contents of your presentation you might be better off making a movie from the
beginning, using MovieMaker (requires Windows XP). Or if you have access to a
DVD recorder (Panasonic, Philips, Pioneer, and others make them) you can connect
your computer to the recorder, and capture the image as you play the
presentation. This requires a video card that has S-Video out, such as the ATI
Radeon 9600 Pro. All software solutions that I have tested either don't work
(see Bill Foley's reply) or they generate results that just don't play well on a
TV screen. Camtasia does a nice job of capturing your presentation, but when
you play the results on a TV you'll still be disappointed. There's no getting
around the fact that television display technology is inferior to what you are
accustomed to on your computer monitor.
Just my $.025.