This article applies to the Windows SDK for Windows 7 and .NET Framework 3.5 SP1.  Read these other posts to troubleshoot issues with the Windows SDK for Server 2008 and .NET Framework 3.5 or to troubleshoot issues with the Windows SDK Update for Vista and .NET Framework 3.0.  

The Windows 7 SDK is available for download in ISO or Web Setup format.  Web setup allows you to select a specific subset of the SDK so you do not have to download the entire SDK. The ISO setup allows you to download the entire SDK to burn to disk or a virtual drive, and install later. This release provides three platform-specific ISOs.  Choose the ISO that matches the CPU platform (x86, x64, or Itanium) that you are installing on.  If you are having problems downloading the correct ISO from the Microsoft Download Center, use these direct links:

Running the Windows SDK web setup on some connections can sometimes have issues when downloading the files. We recommend that you clear the %temp%\sdksetup directory and retry your web setup. If that fails, switch over to the ISO setup for the Windows SDK. 

Typical %temp%\sdksetup directory:

On Windows Vista or Windows 7: C:\%user%\AppData\Local\Temp\ SDKSetup_7.0.6918.0.log
On Windows XP: C:\Documents and Settings\%User%\Local Settings\ SDKSetup_7.0.6918.0.log

About ISO image files

Many products are posted as ISO image files.  An ISO file is an exact representation of a CD or DVD, including the content and the logical format. ISO files end with an .ISO extension.  The most common use of an image file is to write it to a blank CD-R or DVD-R. ISO image files can also be opened and their contents copied to a local folder, much like ZIP files. ISO files may also be virtually mounted and accessed as a device. These two methods of using ISO images are described below.

Copying the contents of ISO files to a drive

The contents of image files can be used as virtual discs using utilities such as ISObuster, Daemon Tools or Virtual CloneDrive for Windows. Using this method you can extract the files from an image file to a temporary folder on your hard drive, then run setup.

Writing ISO files to CD-R or DVD-R

Most CD-R/DVD-R writing software includes a feature to create a disc from an image file. Note: you must use the special "copy image to CD" or "burn image" functionality. See your software’s Help for detailed information. Common utilities for writing ISO file to recordable media such as DVD-R include Nero and Roxio. In Windows 7, you can burn and ISO by right-clicking the .iso file and selecting “Burn disc image”.  After a CD/DVD-R has been written, you should verify that the file was successfully written. Many freeware programs are available for calculating the SDK SHA-1 hash value.  Use an Internet search engine to search for “sha1 hash” to find a freeware program.  Windows SDK for Windows 7 verification information:

File Name: GRMSDK_EN_DVD1.iso
Chip: X86
CRC#: 0xCA4FE79D
SHA1: 0x8695F5E6810D84153181695DA78850988A923F4E
File Name: GRMSDKX_EN_DVD1.iso
Chip: AMD64
CRC#: 0xB417A4F7
SHA1: 0x3393C98B8468CB3505557854922707510F8B65E1
File Name: GRMSDKIAI_EN_DVD1.iso
Chip: Itanium
CRC#: 0x5E0E4BEA
SHA1: 0xAE454215585A044EBE593E9F71FF1A4BC03D56A8

Other Resources

Windows SDK Online Release Notes

Windows SDK blog

Windows SDK MSDN Developer Center

Windows SDK Developer Forum