I don't have an Xbox 360, but I would think you have to tell it to run in 720p mode somewhere in the dashboard, not just connect the component cables. Also, not all games will necessarily support 720p, and I'm not sure the 360 will upscale games.
Okay, so I bought this TV from newegg:
However when I hooked up the cables to the TV with the 360's HD cables and play up in the corner it says "YPbBr - 420p SD"
Can't I play this in 720p?
I called up their support since I don't know barely anything about TV's and was wondering if I could play my 360 in HD but the lady said that the signal is all ready digital so it can't be HD...is that right?
Basically any help would be awesome, thanks everyone!