8 beep sound in inspiron N5010

Hallo,

 I have dell inspiron N5010 model laptop.From last one month it has started giving problem in booting.It creates 8 times beep sound while starting.If i keep shift+del+Cntl keys simulatanously pressed for longer time then some times it restarts normally.Some times during working also it suddenly gives black screen and  restarts with black screen and creATES same 8 beep noise.I have shown to local mechanic and he has done something it afterwhich laptop wokked for 2 weeks and same problem started again.I am really confused about dell's product.I dont know is the problem of hardware or software? Also why this is happening about Dell only?So please help to solve this problem.