Just a week ago, Microsoft was sending out invitations to a select pool of early adopters informing them of the imminent availability of Windows 7 Service Pack 1 Beta and Windows Server 2008 R2 SP1 Beta for testing. And, now, it appears that the Redmond company has already started serving the first Service Pack 1 bits. Various third-party sources claim that the software giant is currently offering the development milestone to a limited number of early adopters involved in the Beta testing program. (via WinFuture)

7601.16562.100603-1800 is reportedly the build string of Windows 7 SP1, indicating that this specific Build of the service pack was wrapped up on June 3rd, 2010. Still, Microsoft has yet to confirm officially whether 6.1.7601.16562.win7sp1_beta.100603-1800 is the official Beta development milestone of the first upgrade for Windows 7.

According to details leaked in the wild, Windows 7 SP1 Beta Build 7601.16562.100603-1800 weighs in at 1.22GB and is available in German, Spanish, French, English, and Japanese. In fact, Microsoft has already warned testers that they can only deploy SP1 on certain localized versions of Windows 7, in an article titled “Why am I receiving a message that ‘Windows has detected unsupported languages files’ when installing SP1 Beta for Windows 7 or Windows Server 2008 R2?”

“Service Pack 1 (SP1) Beta for Windows 7 and Windows Server 2008 R2 can only be installed on a computer that is running a German, Spanish, French, English, or Japanese version of Windows 7 or Windows Server 2008 R2,” Microsoft stated.

Service Pack 1 comes as a single release for both Windows 7 and Windows Server 2008 R2, being only tailored to the flavors of the two operating systems, 32-bit (x86), 64-bit (x64) and Itanium. However, even though the two platforms share the same service pack, the upgrade experience is bound to be different. Whereas Windows 7 SP1 will bring no new features to the table, Windows Server 2008 R2 SP1 will not be limited to a hotfix and optimizations package, but will also introduce Dynamic Memory and RemoteFX.

Microsoft is planning to release Windows 7 SP1 to the public by the end of July 2010, but the company failed to provide a specific delivery deadline, or any additional details related to launch. Users that are not currently part of the technical Beta program will need to exercise their patience a tad longer before they will be able to get their hands on the Windows 7 SP1 Beta.