There is hidden Aero Lite Theme discovered in Windows 8 Developer preview version for low-end hardware users which is similar to Aero Basic theme in Windows 7,  you can enable Aero Lite Glass  theme in Windows 8  easily, here is how.

Aero Lite Windows 8

Enabling Aero Lite Glass Theme in Windows 8

Navigate to Windows\System32 folder and run WindowsAnytimeUpgradeResults.exe.


You can also enable Aero Lite by running freeware portable Windows 8 Aero Lite Tweaker. You can download this tool from here.

Windows 8 Aero Lite Tweaker

You should backup your theme before enabling Aero Lite Glass  because there is no way to disable this once enabled.