With few weeks left for Windows 7 RC to be released, some Neowin users have found Windows 7 build 7057 in the wild. The build string reads - 7057.0.x86fre.winmain.090305-2000 which means that this was compiled on March 5.
The EULA reads this for now
Yes, this makes it clear that Microsoft is already cooking its Windows 7 RC builds (not final build though)
The most immediate change users would notice is the new welcome and shutdown screen