Can't format Pen drive?

1) Right click on My computer > 

Open Manage.
2) Select Disk management.
3) Right click on disk label 
(like J: etc..)

4) Change Drive letter and paths.....
5)  Click on Remove.
6) Then format pen drive...
7) After that again 
Add Drive letter (J:)
Now your pen drive is safe formatted.








If you still unable to format USB Drive
1) Open command prompt(Run->cmd).
2) Select drive letter for USB Drive(Here it is M:).

3) Type format X (X = USB Drive letter):
4) Press ENTER.