Welcome to the TH community, Soumya Sankar!
I'm really sorry to hear about your WD external HDD!
Good job with the troubleshooting so far! I'd recommend you to try using a different USB cable with the drive and maybe a different port on your computer as well. Another thing you could try is updating the USB hub controller drivers from your motherboard manufacturer's website. (Find your mobo model and check in the available drivers & utilities for your system)
If it's recognized in Device Manager at least, you could try running the WD's Data LifeGuard Diagnostics for Windows and see what is the health and SMART status of the HDD. Here's a link to the WD software, just make sure you run the QUICK and the EXTENDED tests:
http://support.wdc.com/downloads.aspx?lang=en
Keep me posted!
SuperSoph_WD