Neowin.net reports that an early build of Windows 7 Service Pack 1 has leaked to file sharing sites this week

The build, 6.1.7601.16537.amd64fre.win7.100327-0053, appears to be a recent compile from March 27. Early reports, from enthusiast site GeekSmack, indicate the build is quick to install but it's not clear whether it includes the promised USB 3.0 support or enhanced Bluetooth and Wi-fi stacks.

Early Windows 7 SP1 build leaks