Asus x51r powers on then off, no display

Just wanted to confirm a few things..
Did you do a hard power down by holding the power button down for 5 seconds or by just briefly pressing the power button (which would put the computer to Sleep).
I've found this laptop occasionally does not properly recover from Sleeping under Win8, that's why I ask.
Either way, do a hard power down by holding the power button for 5 seconds.
Unplug the laptop and find the battery disconnect pinhole switch underneath (indicated with a picture of a battery lifted up) and using a paperclip press and hold for 30 seconds.
Try powering on again, do you atleast get the Acer logo appearing when powering on?
http://electronicshelponline.blogspot.com/

Power Options

The power switch turns ON and OFF the Notebook PC or putting the Notebook PC into sleep or

hibernation modes. Actual behavior of the power switch can be customized in Windows Control Panel

"Power Options."

For other options, such as "Switch User, Restart, Sleep, or Shut Down,"

click the arrowhead next to the lock icon.

Restarting or Rebooting

After making changes to your operating system, you may be prompted

to restart the system. Some installation processes will provide a dialog
box to allow restart. To restart the system manually, choose
Restart

Unplug from AC, remove battery, plug into AC , boot normally.

It could be problems with display inverter, Memory modul`s or faulty video chip.

I first wanted to turn it on through Atheros Client Utility, but the "enable radio" button was disabled for clicking, so I tried the integrated Windows solution and that didn't work.

Then I reinstalled Windows and all the drivers and Atheros AR5006EG is recognized, but I can't get it to scan wifi networks.

FN+F2 doesn't do anything, the wireless button next to the Power button also doesn't do anything, and the button light is off. It is suspicios to me that the Zzz light (for sleep mode) is always on, even when the computer is running fully.

What do I do?

The backlight driver could be going bad. The ballast control board most likely is the culprit.

Many laptops use a small, 3 cell rechargable battery. Look for something that looks like a small tube lying horizontally. It will be soldered in if that type. One source for replacements, is www.mouser.com
If a replaceable coin cell, then it will be like a watch batter, and quite visible.

Here's the link for all ASUS Drivers

Hardware user’s manual for ASUS X51R.

It is possible that you switched off the internal video display, enabling the external adapter. If this is the case, you should be able to plug in an external monitor, get your display back, and change monitors back to the internal one via software (display properties).