I want to build a home theater in a existing bedroom?

You will need to fish wire from the video source devices (e.g., DVD player, cable box, etc.) to the location in the ceiling for the front projector. This will require at least two holes in the walls. It really depends where you are putting the sources in comparison to the projector. The projector itself will attach to one of the ceiling joists. If done correctly, you will only see a a small piece of the wires coming out of the ceiling and into the back of the projector.

Usually the best way to conceal wiring is to cover it with a flat, rectangular plastic strip, that is designed for this purpose and is available in most hardware stores.

Also, if you are using a DVI cable, you now do get them in transparent covering, which is less visible.

Sometimes a simpler solution is place the electronics next to the rear wall instead of under the screen. That way, you are only running speaker cables, which are easier to conceal, because they can run along the floor.

might check into some of the wireless speaker systems, not as good as wired but i know some use 900MHz to 2.4GHz transmission and some actually use a infrared beam to send data. Just an alternative. I have three receivers in one room and i know about the wiring mess. :)

Cut a hole in th wall the size of the TV or u can hire a contractor and u cut a hole the size of the TV, buy a fla6tscree and put it like in the wall, and to make it look nice tou can put interior and a glass case on and around it.

call a local electrician and he should be able to install it for ya (for a price). it would not say its necessary to tear down the walls, but a quite of bit of wiring is involved