Dell laptop stopped working!

Hi,
I have a 15 month old Dell Inspiron 15R 5547 laptop which was working fantastically well until last night. I connected it to a USB charging wire to a modem and suddenly the laptop died. Don't know if it was a surge or something. Now my laptop doesn't power on at all. This is what I have tried:
1) taken the battery out, done held the power button for 2 mins to discharge it and reconnect the power supply.
2) removed the ram, hard disks
3) The usb sockets seem attached so I can't disconnect the ones on the left, but the ones on the right are powered off the board and disconnecting them didnt work.
4) left it overnight and tried again.

When I connect the power supply to the laptop, there is this strange loud buzzing noise which is coming from the fan or processor. The fan doesn't turn on, and there is no dirt in the fan. When I connect the battery (fully charged) the laptop doesn't turn on, but this noise doesn't come either.

Please help me out here. I really hope the motherboard hasn't died, as I paid a lot for this laptop and its run out of warranty only 3 months ago.

Thanks