don't HDMI cables carry both audio and video?
They can, but his computer/TV may be old. I'm sure his TV will have a RGB or S-Video port, so he'll just need one of those and an audio cable. After those are connected, then he'd just activate the screen in his computer settings. Et voila!
S-video will look like crap on any large/HD-style screen. You'll barely be able to read text, but it'll work OK for looking at videos. RGB, DVI, or HDMI are the best options.