Problem while opening the laptop

Registration date
Monday September 10, 2012
Last seen
September 10, 2012

sir i have purchased dell laptop having the 4gb ram. 500gb HD and 64 bit os with intel core i5. model no N4010.
It worked satisfactorily but last two days when i switch on the system it is making the ALARMED sound loudly till booting. sometimes it take 10 min to boot. if i press the F12 key it stops the sound. once the windows started then there is no problem the system is working nicely without any interruption. kindly tell me what is the problem and how can rectify the problem. i am using the windows 7 home basic.