There is a way of achieving what you want, but it unfortunately changes a number of other visual features.
I take it that this is what you want to disable:
To do this, click on the Start Orb
and select Control Panel
. If you are in Category
view, click on System and Security
. Next, click on System
and then Advanced system settings
(note that you will have to provide administrative credentials to continue). The option you require is Use visual styles on windows and buttons
and you need to deselect (clear) the checkbox. Finally, click on OK
and close all dialogue boxes.