Your 6 yr-old couch potato doesn't seem to understand that he can't watch TV and videos all day, every day. He's getting square eyes and you're getting stressed.
Your child wants to watch TV because TV is fun. It's not unhealthy to enjoy television but the trick is to make it a (minor) part of a range of activities. Too much TV can stunt his imagination, affect his physical fitness and limit his social skills.
Why does he watch?
Is he glued to the box, or does he put the video on and walk away to play? Perhaps he likes the music. How often do you have the radio playing while you do something else? Put on the CD or cassette player for him instead.
Set a good example and limit the amount of TV you and your other children watch. Never eat in front of the TV and try to make viewing a family activity. If the family are watching one programme and he wants to watch another, be firm; say 'no' and explain why. Distract him or take him into another room.
He may be watching TV because he's bored. Find a distraction, and then turn the TV off. Don't leave it playing in the background while you do something else.
No TV, no problem
If it's not there, it's not an issue. Unplug the TV or move it to a less accessible place. Your son will find something else to do. If he doesn't have brothers or sisters to play with, invite another child over to play with him after school.
Take time out yourself and do something together. If you have to cook the dinner, let him come to help you. Cooking can be fun - and maybe he's seen some good cookery programmes that he can tell you about!
Don't ban TV altogether
If your son loves television, use it to your advantage. He can learn a huge amount from television and it can spark his imagination. Books that are televised become best sellers. It doesn't have to be a diet of nature and educational shows - use the programmes that he likes, to introduce ideas. Watch plays and children's TV together, there will always be something to discuss.