Laptop won't work without LCD attached?

[StockDC2]

Hi, I have an Alienware M17X R3 that has been disassembled for a project and while giving it a test go, I could not get the computer to do anything else but turn on. Nothing displayed on my monitor, none of the activity lights lit up, etc. Heck, the fans didn't even spin. After attaching the original LCD onto the motherboard though, the computer operated just fine.

Is there a bypass that must be done or does the LCD have to be attached at all times?

Thanks in advance.