The three lights are the Power Light, The Wifi light?, and the HDD light. Does it turn on at all? Or does it giving you some type of error when you start up?
If it doesn't turn on at all, try plugging it in and try it. If still nothing, remove the battery and keep it plugged in. If it works then, your battery is shot/dead and you need to buy a replacement. If still nothing then try using a different charger if you have it. If the new charger works then you have a bad charger.
If you get an error message, such as there's no BOOTMGR or OS installed then your HDD has gone bad/is going bad and you must replace it. The HDD light is dull because it flashes when the HDD is in use; an activity indicator.
If it beeps at you continuously, then your RAM might have gone bad and you'll need to replace that.
If all else fails, there's probably some faulty hardware in your Laptop (probably the motherboard) and if you still have a warranty on it you should ship it back and get a replacement.