I have finally fixed the MX7515 problem. The culprit was the processor. I finally got my hands on a desktop socket 754 CPU and installed it. Lo and behold, I powered it on and it turned on. I turned it off and connected an external monitor and turned it back on – we have LIFT OFF.
So, in the case that you ever come across or have yourself a Gateway/Emachine notebook that exhibits: Turn computer on, blue indicator light stays on for five seconds, blue light turns off and you can hear the hard drive turning off, and then blue light turns on one more time except no video, you probably have yourself a bad CPU.