The disk in use percentage bars can be alarming and inaccurate particularly for automatically connected network shares. Therefore, I find it is best to hide those from windows users on lab/classroom computers.

Open REGEDIT and navigate to: HKLM\Software\Classes\Drive
Right click on “TileInfo”. Remove the phrase “System.PercentFull;” from the string

For more details see:
http://www.instantfundas.com/2012/11/how-to-hide-drive-space-indicator-bars.html