Disable NickName in edit profile?

When a user goes to edit his/her profile, I want them to see their NickName textfield, but I want the box to be disabled (read only). How do I do this?

The user cannot can edit the nickname in v6.1.4  .....  what version are you using  .....  ?

$site['ver']               = '6.1';
$site['build']             = '4';

they can on my version of 6.1.4

go to admin> builders> field builder> edit profile> owner radio button and remove Nickname block from the active blocks