How to open Sony Vaio PCG-4G1M?

Question

When I did unscrew 7 screws and 3 additional from under the screen there is still something holding it together from the center. Can't find the problem. 2) How to know if power needs to be changed (I suspect it blew up) and how to do that? Got the puter from a friend who described as if something blew up. It is dusty and small, the friend had no mercy on a thing. So, I am just playing with it. But if it is possible to fix it on my own I would be most excited! :)