Is the hard drive still seen in your BIOS?

I'd be careful doing this, because of your warranty, but have you tried putting the HDD in another laptop and seeing if it is detected. Also, you can get specialist leads that enable 2.5 disks to be read in a standard PC.

Dell support should be your first option though.

If the drive isn't seen by the BIOS, your only hope is a data recovery service.

The Hard Drive is not seen in BIOS. If i need to connect the Hard Drive to another Laptop/PC to see whether it can be detected over there..How to do that?

If your hard drive is not seen by BIOS and then there is little point in trying to slave it to another computer as it will not be seen.

It is most likely that an IC circuit has failed and usually the only way round that is to substitute the circuit board from an identical hard drive onto the old drive. This is what the recovery services people do!