Windows/Visual Styles/Aero Lite
"Aero Lite" is the name of the new low-end theme in the upcoming Windows 8. It replaces both Windows Basic and Windows Classic.
An aero version of this theme (with glass) is hidden in Windows 8 build 7989 but it can be unlocked in two ways.
Aero Lite ('Windows Basic') is also in Windows 8 Build 8102, 8250 and 8400. Transparency can be enabled in the Consumer Preview and the Release Preview by way of a bug in the Personalization control panel.