This laptop was working fine, all the sudden it shut down. I took the hard drive out and put it back in, I took the battery out and put it back in and the computer started again. Then after a while using it, it shut down again, this went on for about 6 or 7 times. Last night it did it again but this time is not coming on at all. The ac charger is connected you press the on button and small led light to the right come on and off but nothing happens. Could this be the mother board?

Did it by any chance over heat? Laptops are not well vented and if you do not leave the vents uncovered then they will overheat and shutdown. It takes a wile for the to cool off. Also check and see if the fan for the CPU is working. You should be getting air out of one of the vents. If not send it for repair.

No, it did not overheat, I was verifying the fan, in addition I added a cooling base that has twin fans. The interior fan in the computer was also working fine. The laptop still doing the same thing.

Any activity or lights on the system?
You said the led comes on to show it is getting power does the HD led show any activity?
Do you have an external monitor you could hook up. Could be the display is going out or the wires connecting to it are breaking.
When you say it shuts down what do you mean? DO all the led's go out, is the fan still running, do you see any messages?
If you get it running again and it is a windows system then see if there is anything in the event viewer (Control panel, Administrative tools, Event Viewer) and look in the Windows System log for errors.