Freezing and hangign up problem

I have a dell n5010. since the beginning there was a problem. the laptop was locking (freezing) for few seconds with no responding to any process, then it began to work sending this message: display driver stop responding but it recovered successfully.

after a while it became worst. Now the laptop suddenly freezes completely (unregarded to the program which is running or the duration of using (time)), and doesn't respond at all so I have to shut it down by pressing it's power button.

I have formatted it's hard drive and have installed updated drivers.

Help me plz