Step 1: Materials and Initial Disassembly
LCD Monitor, any old one will do, the backlighting is going to be ripped out anyway. In my case, 14" was perfect, larger would have gone outside the border of the overhead's window.
Overhead projector, like from school. I'm no expert at these, and living in Taiwan, it was nearly impossible to find, but I know there are loads on ebay for cheap.
Document protector, used for housing the power and settings strip of the monitor.
Cork. Self explanatory.
First, get the LCD glass out of the monitor by carefully unscrewing, dismembering and prying. Be careful around the wires and you should be fine. One handy thing is that on mine, the display cable was detachable from the motherboard, so that made it easier. It's helpful to have a second pair of hands for this, in my case, I used my girlfriend's.
Step 2: Initial Assembly and Test
I found that my projector was overheating and shutting off by itself, so I mounted a fan on the inside of the casing to get the air moving a bit.
Step 3: Casing
After a brilliant suggestion from Alyosha, I have since created a bellows as a variable-height enclosure. I will be posting a separate instructable for it presently.
Step 4: Finished!
I have just finished creating a bellows that serves as a wonderful variable height enclosure and keeps the light spill-off to a minimum. See step 3.
Overall, the project was pretty simple, and it works great! I'm going to be making a rear projection screen for it, which I'll post a separate instructable for as soon as I finish.