Updated with the latest information.
As promised, Microsoft today officially released Service Pack 1 for Windows 7 (all editions) and Windows Server 2008 R2. You can find it at the Microsoft Download Center.
If you only have one or two PCs to upgrade, I advise waiting until the installer shows up on Windows Update later today. I’ve just completed the installation on a test system here; it went very quickly.
The Microsoft Download Center requires validation; after you pass that check, you’ll have the option to choose from multiple versions of the Service Pack code. The ISO file (7601.17514.101119-1850_Update_Sp_Wave1-GRMSP1.1_DVD.iso, 1953.3MB) is for IT pros who want access to all three SP1 installers in a format that can be burned to DVD. Most users will also want to ignore the four symbol files, which are for use with debug versions of Windows.
You can download separate installers for 32-bit and 64-bit Windows 7 versions
- 64-bit: windows6.1-KB976932-X64.exe, 903.2MB
- 32-bit: windows6.1-KB976932-X86.exe, 537.8MB
The Windows Update package should download automatically overnight. If you want to force it to download and install now, open Windows Update and select the check box next to the Service Pack 1 entry, click OK, and then click Install Updates.
If you’re getting Windows Update errors, try using the online fix-it tools available from Microsoft. Details in this ZDNet post.