Sounds like an interesting project.
Grab a 15" to 19" screen, pick up a touch screen kit from ebay and do your thing with the screen, buy a miniITX motherboard like this one
. Now, you can get that one or, one with an Atom cpu in it which will be thinner because of the larger heatsink needed for the proper lga775 cpu.
Then get a PSU (smaller ones made for miniITX are better for this), get a laptop slim dvd drive and notebook hdd and assemble to the back of the screen. (Try to magnetically shield everything too.)
Welcome to the forums....