Microsoft recently announced that those running legacy platforms must install certain updates to provide support for SHA-2 hash values. Windows 7 and other legacy platforms use SHA-1 to compare hash values of the code. When an update is downloaded from Microsoft, it comes in parts that are recompiled together on the computer.
If all the pieces match the expected SHA-1 hash values, then the update is approved for installation. If the SHA-1 hash values are not proper, then those parts of the update are flagged to be redownloaded and compiled again.
