It seems that Windows 7 Service Pack 1 is leaked and available for downloads.GeekSmack has share this news,and also posted some screenshot regarding the installation of this leaked beta SP1.
The complete build number of this bta Sp1 is 6.1.7601.16537.amd64fre.win7.100327-0053 which means this built is very latest,because as per built it was complied on 27th March 00:53 AM.
The installation process is similar to Windows Vista but a little bit faster.
As usual you can find it on various site like on TORRENTS but we strongly recommend you to NOT TO DOWNLOAD ANY LEAKED VERSION, because it may contain malwares Or adwares