What exactly are you planning on doing? It will be an arduous task to get everything to work outside of the laptop case itself. You'll have to figure out what the power requirements are, as c12friedman said, and then figure out if it's feasible to even try to rig something up to power it.
Then you have to figure out how to actually turn it on, since there won't just be a button for that, unless you can figure out how to take the power button out of the case and put the leads back in into the correct place on the mobo (if that's even possible, though I suspect that it should be).
In any case, it's a lot or work for something may not even work the way you think it will. Obviously, you'll have to have a monitor hooked up to it, since the LCD from the laptop can no longer be used, as well as a keyboard and mouse because and you won't be able to use the keyboard and touchpad from the laptop.