Hi. sometime blue screen appear on my laptop and it automatically restart after that... i dont have enough time to jot down the problem detail sicnce the blue screen disappears in seconds.. this usually happens when i am watching movies for too long.. can i know what is the problem of my laptop??

and sometime if my laptop is overwork, mean i on my laptop for too long, like 15 hours a day, a white tiny light will keep 'splashing' at the bottom of my screen, until the screen becomes normal again after a few minutes. but i still can see clearly what is on the screen when the white tiny light is there.. what is the problem of this??

thx thx..