case sensitivity of the login is a function of the way the MySQL Database is created. it is determined by the chartacter set and collation settings for the rtable.
the default character set and collation settings in MySql are latin1 and latin1_swedish_ci which result in none case sensitive string searches.
to force case sensitive string searches, the collation will need to be changed to latin1_general_cs or latin1_bin:
you can edit the collation using PHPMyAdmin or another GUI tool.
In PHPMyAdmin, open the database, select the users table and go to the Operations tab, on the Operations tab you can change the collation used for the table.
next go to the structure tab, and select the username and password columns, click the edit icon to edit them and set the collation for those columns as well.