Quick info:
“Adminimal Administration Menu” changes the style of the
“Administration menu” module. It adds a nice and simple minimalist look and
provides some tweaks to improve you Drupal administration experience. 
The menu hierarchy is not simpler and easier to understand
(removing the unnecessary transparency and only highlighting the correct menus).
 It also adds shortcut links that can be edited from the core shortcut module. 
 The shortcut links fit nicely and have a small icon that separates them from
 the normal admin menu links.

Requirements:
Requires the administration menu module (http://drupal.org/project/admin_menu) 

Installation:
1) Download and install like any other drupal module
2) Enable the “Administration menu Adminimal Theme” from the module manager. 
If you are using the “Administration menu Toolbar style” it will be disabled
automatically to prevent some styling issues. This change will be saved in your
database, so if you decide to disable the “Administration menu Adminimal Theme”
your old “Administration menu Toolbar style” will be enabled automatically
so you have nothing to worry about.
3) Refresh your administration page and you must be good to go!