This is highly bizarre. My computer refused to start up one day, so I unplugged everything (including the power) and it decided to work. I plug the power back in, and the thing shuts off in about three seconds. I tried a friends power cord to see if that was the problem, same deal.

From some testing, I've figured that the problem only occurs when my computer is both turned on, and plugged in. When this hapens, it shuts off after  a few seconds.

If it's off and plugged in, the battery charges as normal.

With the computer turned on and running on the battery, everything is perfectly fine.

My friend tells me that it may be a problem with the voltage regulator. Can anyone tell me more? Thanks.