If you want to evaluate the desktop Windows 8, but the system itself does not really want to set, you can try to download this service pack. Windows 8 Transformation Pack will transform your Windows 7/Vista/XP user interface to Windows 8, including the boot screen, logon screen, themes, wallpapers, icons, sounds, fonts, metro / modern user interface, Auto-painting Aero, UserTile tray and more.

After installing the package will change Boot Screen, login window, the theme and wallpaper, icons, sounds, will be added to Metro UI, the task bar will also change, in general pretty much everything, you are sure you will be impressed that installed Windows 8.
The developers recommend to put Windows 8 Transformation Pack on a clean OS, as some programs may refuse to work.

What's new in version 7.0:

Added WinMetro as alternative Metro Start Screen
Changed default Immersive UI to Metro Start Screen (WinMetro)
Improved sounds scheme files handling method
Updated Font installation code based on recent patch
Updated Glass UI theme configuration based on hacked Aero Glass in Windows 8
Updated Windows 8 Media sound scheme files and resources
Updated Windows 8 visual style for Windows 7 by Rammist

System requirements:

Windows 7 / Vista / XP (32 & 64bit)