Entertainment Center: TVs, Stereos, VCRs and DVDs - Zenith HD tv inputs don't work

I have a Zenith HD tv, only two years old, hardly used. I haven't used it in months and now tried it out. The over the air TV shows look fine but when I try to use the RCA and component inputs on the the back, they don't work. I get a black screen and no sound but the input information shows up on the screen, like video 1. The manual say it's for model numbers C27V22, C32V22 and C36V22. I tried unplugging it for a few hours to reset the software but that didn't help. Is there something I can do to get the inputs working? If it sounds like a repair job, what would that be for and would it be expensive? Thanks in advance for any advice.

What are you using as a source for your video?
some cable boxes and sat rcvrs have to be programmed in the settings menu to output from the component outs.

and are you sure you are on the right input (input 1,2,3) on your tv?

also, some tv's have the ability to turn off inputs in the settings menu.

just throwing out some things to check

For some reason, the input on the front of the tv works fine (I just tried the RCA inputs, not the s-video one) but the back ones aren't working. I tried hooking my DVD player to the back of the tv at the HD input with the composite cables, my VCR with RCA cords to the video 1 input. Nothing. I'm sure I connected them correctly. I used the button on the remote that goes through all the inputs and antenna. Just the antenna and the front input work. Could I need to switch something in the DVD player, from analog to digital, or something? That wouldn't explain why the video1 input doesn't work. Any ideas?

HD won't work on s-video nor composite cables. HD needs component, HDMI, or DVI.

Yes, the DVD player needs to be set to either digital (progressive scan/480P) or analog (480i). But that also has to match the cables (see above).

^ Exactly what Bob said!!!! You can never get HD signal through a standard RCA input or S-Video.

It's working again. I messed up. I had the yellow video RCA plug in an audio input by mistake and corrected it. Now it's working fine. Thanks for the advice.