my book external hard drive help pls

i have this western digital external hard drive it used to work when i just plug it in the usb but now for some reason my computer just cant find it:cry it has no installation disk with it coz the way it works is just plug&play i also checked all the cables if its loose but still not working help plss:cry

 

Oftentimes, USB storage will try to take drive letters that are already in use, and that makes them "invisible".

Here's how we find it:

1. Plug in the HDD, and power it on.
2. Right-click 'My Computer'
3. Select 'Manage'
4. On the 'Computer Management' window, click 'Disk Management'

Here we will see a list of all disks mounted on your system. One should correspond to your hard drive. Check what drive letter it has beside its name. Is it one that is already in use?