For an HD feed hooked up using component cables (red, blue, green) that is HD but you must set your HD cable or satellite box to 16:9 output and your tv settings must match. Also, if there are composite cables [(Audio:red, white) Video yellow] make sure that your tv is set to the proper Input as well and not taking the SD feed instead. These are all common mistakes that keep people from watching what they are paying for, HD! There is a massive difference in both picture and audio as the audio levels in particular will be much different when you go from the SD feed to the HD feed. For visual difference, look at the graphics on screen, SD will stretch and often cut off graphics or move bugs to the far corner of the screen and make them bigger.