Dell inspiron 15, won't switch on and beeps

I have a dell inspiron 15 3521. It works sporadically recently, I switch it on the hard drive light comes on? (One like a can shape) briefly and then goes off and it starts to beep constantly with roughly a 3 second interval, I bought this laptop in April 2013 and now just under a year out of warranty. What can I do to fix this. Tried removing ac and battery and pressing power for 15 seconds tried fn + power button, this also doesn't work and tried d with power, didn't work. Please help!!