Usually with a laptop people jerk the cord out of it when plugging it in.
They either break the ac adapter itself, or the jack inside the computer itself.
Try to switch your adapter for a buddies, and see if that works.
If not then I would look at replacing the jack…
You can buy a jack for nothing on ebay, put soldering one onto the motherboard is not fun. I don’t even do a service like this.
Laptops cost like 500 bucks now, and come preloaded with vista, might be time to cut your losses.