Hitachi 32CX39B When my tv was turned on, everything was fine, but when the xbox got turned on, only a horizontal strip showed on the screen. I tried unplugging everything, and there is still only a horizontal strip that shows part of the picture. One of my room mates said that he hit the top of the tv a little bit, and then it went back to normal. But, now it's just a horizontal strip. There's sound on the tv, but when my dvd player is plugged in, the sound is distorted.

The solution by jomaru is what I would suggest, but in addition the fault may be a bad connection in the power supply regulator chip, giving a low voltage, which may also affect the sound quality. This will need looking at by a local service engineer using at least a meter. Inspect the component boards for burnt resistors which sometimes fail. If the copmonent is located and changed but fails again, a service engineer must be called, beware of high voltages.

The xbox is just a coincidence,the good thing is your friend tap on the set and it reacted going back to normal maybe for only a second but is good,you have a loose conection is the vertical IC,this the circuit in charge of pushing the picture up and down.The vetical IC is normally mounted in a small heatsink and is flat,it should have 10 pins soldered to the board.The board need the be flip over and the pins resoldered. If you are familiar with tv service you have a place to start but if you are not too familiar be safe and call for assistance from a servicer.Let Us know how it goes and if you need more information.