Desperately need help. I have a 2 year old 15" macbook running on a snow leopard i let it open overnight for about 8 hours because i'm downloading something. I turned it off then turn it on after awhile it freezes on either grey and blue screen. I tried using disk utility, it says hard disk appears to be ok but the problem is still not fixed so I reinstalled the snow leopard using dvd installer..ganun pa rin siya. Anyone, please help.