Error 1329 installing the Windows SDK

This is an error that several users have reported and looks something like this:

Error 1329. A file that is required cannot be installed because the cabinet file C:\WINDOWS\Installer\MSI122.tmp is not digitally signed. This may indicate that the cabinet file is corrupt.

This error usually comes from a download component that has gotten corrupt
in the process of downloading. All files in the SDK are fully
code-signed and tested. If you get this error again, clear your IE cache and
retry. If you continue to get it, download the ISO version of the SDK using
a download manager. Then follow the instructions on the page to run a CRC
check, verify the bits are good, then install the SDK using the Virtual
CD-ROM Manager utility included on the download page.

The red flag for us on this error is the location c:\windows\installer\*.tmp. Because this is a temp file created when the MSI uses local resources, it should automatically inherit the properties of that MSI. If an MSI is signed, there's no reason for the .tmp file to fail.