The Windows 7 SDK’s available in ISO or Web Setup format. Web setup let you select specific subset of SDK, to avoid downloading entire SDK. In the ISO setup, you download SDK, burn to a disk or install from a virtual drive. This release provides three platform-specific ISOs (x86, x64, or Itanium). If you’re having problems on Microsoft Download Center, download: x86 GRMSDK_EN_DVD.iso, AMD64 GRMSDKX_EN_DVD.iso, Itanium GRMSDKIAI_EN_DVD.iso. Running Windows SDK web setup on some connections can sometimes’ve issues when downloading the files. Its 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:
Windows Vista or Windows 7: C:\%user%\AppData\Local\Temp\ SDKSetup_7.0.6918.0.log
Windows XP: C:\Documents and Settings\%User%\Local Settings\ SDKSetup_7.0.6918.0.log