This is how I did my friend's ht.
The screen is simply the wall, painted in behr ultra pure white flat interior latex from Home Depot. The screen is a 100" 16X9, the projector is an Infocus 4805.
The black broders are primed mdf 2" or so wide strips you find in the moulding section of HD, usually used as base board trim. They were cut at 45 degree angles around the screen, painted flat black, and attached to the wall using nails.
*Note the image was photoshopped. In bright light the image would totally washed out*
Victor