Xbox 360 green light turns on but it does not work or boot up

I guess you have to get yourself a new xbox or send it to Microsoft if you still have warranty (if you have something like x360key, obivously remove it first). It has nothing to do with the HDMI cable (or any other cable) since you can't connect an controller (you could try another controller).

Does the Xbox do the spinning ring of light on boot? If it does, do you have other screen cables? Did you change screen settings recently? If you have recently changed resolution to a higher pixel ratio (1080p from 720p or 480p) you might need to connect a pair of cables that switch from HDTV to TV and use the TV option for the moment, this will force the 360 to rewrite the config of the resolution and use 480p for standard CRT TVs. Chances are that if you can't get any picture at all form either your HDMI or Standard screen cables that the video component is shot and you would need to contact xbox support. It's rare but I've seen it happen and falls under warranty if the xbox is still in the three to four year warranty.

There is a lot of things that can be causing this. Is your connection cable in right? Is the connections on the Xbox on right? Are you on the right TV input? If using three cables, are the colors on the correct positions? Is the HDMI cable broken? Is the ring around the xbox red? Check them out before submitting for a new Xbox.

Change composite cables (red white yellow) or hdmi connecting to tv. That will fix it because your xbox cables are damaged.