Hey there, Vishnu_B.
I'm sorry to hear about the issues you've been experiencing with your drive. If this a new drive, or an old one which just started having this problem? If it's an old one, do you need to recover data from it? Have you checked if the drive is recognized in Disk Management? If it is, you could try to assign it a new drive letter by following this tutorial:
How to change the drive letter assignment in Windows (it will also show you how to access Disk Management). If that doesn't help for the drive to be recognized by Windows Explorer (This PC, My Computer), you should try the HDD with a different computer (which has a different OS) and preferably with both USB 2.0 and USB 3.0 ports and a different USB cable (preferably shorter than 12"), to see if the same thing happens.
If you don't have any data to recover and none of the above proves useful, I'd suggest that you download DLG (Data Lifeguard) and run both tests (Quick and Extended), to see if anything unusual pops-up. Here's how to do it:
How to test a drive for problems using Data Lifeguard Diagnostics for Windows.
Hope that helps. Please let me know how everything goes.
Boogieman_WD