My Acer Aspire 5100 just went blank. There is a

Remove the main battery, it is probably loading the power supply down. If your computer starts up, replace the rechargeable battery.

Light 'OFF' - you are on Battery
Light 'ON' - you are charging the Battery
Light 'flashing' - Battery BAD.
Time for a new battery :(

hi-I have 2 of these 5100 notebooks-indicator lights are as follows -left is bluetooth next one is wireless lan, next one is power on,and the last one is battery. only way I know is to unplug it when not in usand the light will go off. if plugged in the light will stay on showing charging(orange) and charged (green). me i just put somthing in front of the light to block it from lighting my room at night.yes, they should have made it turn off at full charge, but they did not. good luck with that-hope this was helpful. have a great day!

the battery might be hosed up will it boot without the battery and just plugged to ac - if it wont boot from ac with the battery remover send it to acer

Try removing the battery and running the power directly through the power outlet. HP laptop dv6000 has the same problem.

Go to acer/global support and get the bios update for windows 7 because right now your bios are probably for VISTA:( Once you flash them reboot and you should be able to go straight into win7

Bad motherboard or a failed attempt at a bios upgrade/flash

ACER PICTURE PROBLEM – MY SOLUTION

I had a similar problem, but I got a picture before it broke up and went off. The screen was backlit, but no video (screen was receiving some power).
The LCD needs a very stable voltage to work, this is provided through the LCD connector ribbon. In my case the ribbon was damaged and replaced it.
I have had no problem since.

I discovered this through trial and error; I first changed my transformer power supply and then the video inverter card.

You may find the link below helpful as it contains articles that photographically show you how to open the laptop for repairs.

http://www.insidemylaptop.com/category/1-acer-laptops/

Hope this helps. (Please rate my advice)

It Needs a new Backlight period.(Red hue is clue before complete failure). 15.4" Widescreen? Weve replaced hundreds and some can be a pain.. Run on external monitor until you can get it in for repair.

There are a ton of businesses that can replace these besides us where are you located?

The Aspires should have no issue booting without the battery installed. Have you done a static reset? (i.e. hold the power switch for 20/30 seconds without power or battery in) And the voltage range on the Aspire 5100 should be +19v - +20.5v on the inner part of the connector so it might be worth checking that the power adapter is outputing correctly.
If it works without battery, then it can be checked by testing the voltage between pins 1 and 6 on the battery (the ones either end) and should be 7.5v or above if the battery is charging correctly.
Hope that gives you a starting point, if you've done all those things already then appologies and best of luck with it.