Windows 7 is the upcoming version of Windows and the successor to Windows Vista. Windows 7 is expected to be released in 2010 and includes reworked user interface, however, Windows XP users can download the Windows 7 desktop theme and enjoy the look and feel of Windows 7 before it's release.
To some extent the Windows 7 desktop theme looks similar the themes found in Windows Vista. However, there are some enhancement, as you can see from the screenshots below:
How to install the Windows 7 theme in Windows XP