Some suggestions I found on other sites, try #1 first....remove battery and see if it runs with just power adapter:
1. This happens occasionally when the battery on your notebook is going bad.
Remove the battery and plug the PC in with your adapter. It should run normally, as long as you keep the adapter plugged in.
2. I assume you read the error code by pushing the power button, and
watching the numlock scrolllock and capslock, or any other error codes,
if you find any post them.
do you get a blue screen?post the error code on that it follows the word stop.
if you can pull one ram stick at a time, and see if it starts up then swap ram sticks.
if your power led lights up, try plugin in an external monitor, your lcd might be dead.
3. Does it turn on when you have it plugged in? even if you take out the
battery, it should be able to power up if it is plugged in.
If it does still work then it is the battery. If it doesn't then you probably have a hardware problem.
Try turning it on and hold it up to your ear, can you hear anything at
all when you press the power button? if it makes a noise and then shuts
off shortly after, you probably need a new laptop. if it makes a
clicking noise it could be the hard drive. if it does nothing at all
then it may not be getting power at all.
4. (From consumer complaints at Consumer Affairs .com)
In about 10 months, the laptop does not stay on when even when the laptop was charged overnight.
In 14 months, the laptop just went dead. Per repair shop, the
motherboard is dead. I contacted Gateway they won't repair the laptop
because it is past 1 year warranty.
It is a poor quality product -- dead for only 14months!
And from Gateway: http://support.gateway.com/s/Checklists/BPC/ck2007043065.shtml
And procedure to repair power switch if you have to:http://www.insidemylaptop.com/disassemble-gateway-nv-series-laptop-fix-power-jack/