Windows 7 build 7057 has been leaked. It was compiled just 6 days back and brings a few changes since build 7048.  It'll expire on 02/03/2010.

Few changes in 7057

• UAC Issue : previous build of windows 7 allowed you to change the level of UAC without ever receiving a prompt from the system. It was dangerous from security point of view as a malware can turn off UAC on a system easily. But now it has been  fixed in 7057 build
  
• New Login Screen
   
  
  
• New User Display Pictures
   
  
• New Wallpapers
  
   

About Windows Screenshot :

Thanks to Vishal and Geeksmack for this news and screenshots...