Not able to install a module via drush I am trying to install 
Vote Up/Down module via drush. But even if it is not already installed and it has been downloaded, it is not being installed.

[root@localhost custom]# drush dl vote_up_down
Install location /var/www/html/d7/sites/all/modules/contrib/vote_up_down already exists. Do you want to overwrite it? (y/n): y
Project vote_up_down (7.x-1.0-alpha1) downloaded to /var/www/html/d7/sites/all/modules/contrib/vote_up_down.                [success]
Project vote_up_down contains 5 modules: vud_term, vud_field, vud_node, vud_comment, vud.
[root@localhost custom]# drush en vote_up_down
vote_up_down was not found and will not be enabled.                                                                         [warning]
There were no extensions that could be enabled.                                                                             [ok]
[root@localhost custom]#


Can anybody help me with this?
Project contains 5 modules. Neither of them is named exactly like the project. See the names you were given in first message.

You probably meant

drush en vud