Well, the main problem is that computer IR ports are not exactly compatible with the IR standard used by your TV or VCR. Computers are designed for high-speed, short-distance travel. Remotes are designed for low-speed, long-distance. It's like asking an AM radio to pick up FM signals. They're all still radio waves, they're just not compatible. :-) Generally the only way to get a reliable system is to buy a separate IR emitter designed for the purpose.