External hard disk read but absent

Hello,

when I am putting my Seagate external hard disk into the USB cable, the drive light turns on as it does normally,the green icon at bottom right in toolbar appears as well, but there is no autoplay and the drive is absent from 'My Computer'.It is appearing in the device manager. Explorer is running very slow. The same thing is happening with the drive in every other cable and in other computers as well.

Please give an insight if you can as to what may have happened and what can be done.

Thank you.
 
Back