Laptop doesn't start and there is exact four beep sound comes from it.

My laptop doesn't start ,when i press power button , no Dell logo appears and there is exactly four(4) beep sound comes from  laptop and black screen remain as it is.

I've read your Beep Code Overview, but how can i know what exactly is happened with it?

I've also had problem in my laptop's hard disk, previously , bad sectors have been detected in it but it worked well till now. Don't know why sudden crash appears in it
So, kindly help me out with this.

Thanks in advance.