I'm having dell inspiron n5010. It was working fine until last week. When i start my laptop, it makes 8 beeps with regular interval continuously with  the screen blank . Couple of days back I switched on my laptop and it suddenly started working without problem. The laptop is making the same problem the next day when i switched on. The laptop doesn't work in battery so i removed it and was using it directly from the charger. Please provide some troubleshooting  methods.