I have the internal LCD display disconnected inside my Mid-2007 20" iMac (EMC2133). I did this to improve overall graphics performance on my external monitor, and to save power on the unused screen. While some online posts suggest you need to disconnect the inverter, LVDS and display data connectors, I had success simply disconnecting the display data connector -- it's the one just below the panel that has two T6 torx screws holding it down. My Mac booted up just fine, no diagnostic light issues or other complaints at all.