Laptop batteries are designed to deliver a specific voltage and amperage, and deviating from those can be bad for the device in the long term. However, it is possible to run a laptop off a set of AA batteries, and doing so is a good education in basic electronics.
Electronics weblog FunnyHacks demonstrates in the video above how you can wire AA batteries to an adaptor plug. You'll need to perform some calculation to make sure you have enough batteries to deliver sufficient power.
We're definitely not recommending you do this as a project to power your current device, but it's an interesting educational project to try with an older laptop you're willing to sacrifice if something goes wrong.
Running a laptop off AA batteries [FunnyHacks]