Hi Imtiaz,
Since you have formatted your hard disk it may have lost its allocation properties and would be no longer visible with the other Hard Disk Drives in 'This PC'.
To make it visible you will have to follow the below mentioned steps: (make sure your external hard disk is connected)
- Open Start
- Type - Create and format hard disk partitions
- Open it
- At the bottom of the open program you should be seeing your external hard disk with a long black colored line
- Right Click on it and Select 'New Simple Volume'
- Thereafter a Dialog box should appear asking what kind of setting you would like to apply to your external hard disk, select accordingly (make sure to keep the File System to NTFS).
- After clicking apply you should be able to see your external hard disk along with other hard drives in 'This PC'
Thank You