If it works on an external monitor, it's likely to be your LCD. I would replace both it and the inverter.
Thanks for the response frozenlead. That was my initial thought too, but I'm unsure if a failing LCD could even produce what I'm seeing. I'm worried I'll replace all that and it still wont work because there is something wrong with, for instance, the display ribbon plug in port on the mobo.
If someone could tell me that they know a failing LCD or inverter *could* look like that, I'd be confident.