Hi gauravthaur,
I'd like to assist you, based on your post you may follow the troubleshooting steps below.
1) Did you try to connect the hard drive using a different USB cable? If not, then try to connect with another USB cable.
2) Have you tried to connect the drive through any other USB port on your PC? Try to use another USB port.
3)Did you try to check the drive in Device Manager?
Try the steps below.
1. From the Start Menu or from the Desktop, right-click on the Computer. This will bring up the Computer Management window.
2. Click on Device Manager, which appears in the left-hand side under the heading System Tools.
3. A listing of the devices in your system should now be visible there.
4. Click on the Universal Serial Bus controllers to expand it and see if there is any rectangle usually marked with yellow color or a sign of exclamation.
5. Right click on that and uninstall it and then restart your PC. Now you should be able to see the drive in my computer.
4) Is it showing in Disk Management?
You may visit the link below and follow the instructions there .
WD external drive is not assigned a drive letter by Windows or Mac OSX and data on the drive is inaccessible
5) You may also run the Data Lifeguard Diagnostics for Windows to test a drive for problems. You may visit the link below for the guidelines.
How to test a drive for problems using Data Lifeguard Diagnostics for Windows
Do let me know how it goes?
Good luck.