A great Windows 8 theme for Windows Vista and XP has been released by mufflerexoz.
Aside from a new startorb, it also adds the new Windows 7 Superbar that makes Vista and XP just look like Windows 7.
ViGlance was one of the first Windows 8 themes of mufflerexoz.
You can download it from DeviantArt:
This theme also allows you to have a real Aero thumbnail preview on XP and Vista.
The Start Orb has a stylish new glow effect!