8 beeps ,no display,intermittantly

i have dell inspiron N5010. have been using since 3 yrs.. nowadays its going blank and gives 8 beeps on booting... after switching on and off for 7-8 times it turns on--> works fine for a day or two---> again goes blank and 8 beeps.. occuring intermittantly.. tried connecting to another monitor which was of no use.. i updater display driver for my graphic card, still the prob recurred. i tied to run after disabling ati graphic card  again of no use.. as told in one of the forums i held D key with power button to check BIST still of no use.. wat has to be done now?? pls help