Thanks for the update
Reason why I asked about where the white light was is because I suspected it was the battery charging LED and by your description it would appear o be the case.
If you remove the main power brick and leave the AC adaptor connected do you get any signs of life from the white LED or the notebook at all and likewise if you leave the battery in place and disconnect the AC adaptor any white LED or signs of life at all from the notebook, power button or caps lock flash etc.
Below is copy/paste from a thread over on GTG where I was helping out, the members notebook was also a Dell and the following is what apparently fixed it for her, by turn on I would assume that she means just press the power on button as you normally would.
-> Take out battery
-> Plug in charger
-> turn computer on and let it sit during the night or for a few hours ( it won't boot, just let it sit). For me, I let mine sit over night.
-> restart and give it a try.
I do not understand why it fixed it. I do know that my first clue was that I took out the RAM and it beeped at me when I tried to turn it on. This is the computer telling me there was no RAM in it. People on the internet said this beep notification meant the motherboard was likely okay. From there I started to google searching for black screen + no fan symptoms and solutions and came across that video. That is what worked for me.