My TV allows you to view 16:9 pics on it (it is 4:3) as it has a button to do so on the remote. You end up with black lines top and bottom (see the third pic I put up)

With digital TV, like Freeview, the majority of channels display programmes in 16:9. If you have a 4:3 TV, the digi-box will have an option in the set up to allow you select what display mode you want to view in, 16:9 or 4:3. On a 4:3 TV you select 4:3. If the prgrammes is being broadcast in 4:3, your 4:3 tv will show it full screen, and if it is being broadcast in 16:9, then your 4:3 will show it in 16:9, but with the top and bottom black lines....

But, my point is, you are making the picture smaller doing it this way. So your 21" 4:3 TV only becomes a 17" or 19" widescreen TV (example)

Your still watching the same picture, but if you had a 32" widescreen you aren't losing any size.

To get the same size picture as a 26" widescreen TV you would need a 30" 4:3 tv, as you lose so much picture to black lines top and bottom...