Why won't my hd component cables work for my 360?

Question

So I have my xbox, been at school using a computer screen with my xbox(special cables) and I come back home to my 420p or whatever tv(it's 420 I know that) but my component cord was broken so I needed a new one. Hdtv and tv wouldn't work. So I went to Korea for a week and picked up a cord there (used) for 15$. Now I come back, plug it in and the HDTV still doesn't work but when I plug in the normal TV it works. I tried setting it to 420 and going to HD but to no avail. I get no sound or anything. Not sure what is wrong cause the cord works, I am able to do normal TV mode but HDTV suddenly doesn't work! It did before I went to school, anyone know why?

Answer 1

use your blue and yellow and red plugs, and make sure teh switch is on HDTV.

Answer 2

Have you tried switching it from TV mode to HDTV mode?

Are all your plugs in correctly?

Have you switched the mode on your HDTV to Component(if it has one)?

Answer 3

It wouldn't be something really easy would it?

like on the console end of the cables it has the HDTV or SDTV switch...