Joey inherited an LCD TV and he needs an adapter to plug in from his old coax cable box. Leo says that coax is an analog connector designed largely for over the air antennas, rather than digital, which is what HDMI or DVI is. Leo says it's going to cost Joey more to get a Coax to DVI converter than it would just to get a new cable box. Then he can get an inexpensive HDMI to DVI adapter. He'll also need a separate sound cable. Since Joey also has component, another option is to go from Component to DVI. That's an inexpensive option as well. But then he could end up with sync issues.
Jerry has a MacBook Pro and bought a pair off brand Cinema displays. But the MacBook Pro can't power them. Leo says that MiniDisplay port will do it. But Apple has replaced that with Thunderbolt 2. He'll just need the right cable. Most monitors don't have Thunderbolt. DVI ports are a possibility, but he'll need an adapter to handle it. Monoprice is a good place to look.
John wants to play stuff from his computer to his TV, but it doesn't have HDMI out. Leo says that if you have DVI Out on your computer, you can buy an adapter that will allow you to connect it to your TV. Other options include