Help!

Hi, I would need some help on a compaq presario 900 laptop. The problem is, that when I switch the powe button on sometimes it boots normally then after a while I do not have any display . There after when I switch it off then on again the display does not come on, the harddrive sounds like it wants to boot. It just makes a short niose and then that's it.
My question is: has somebody ever had this type of problem before? Is it a harddrive problem or a problem with the voltage?

Would be very grateful for any advice and help.

Thank you
funny_dayz