MAKEMSI installed a right click option for files which makes use of this tool to calculate a files MD5. An "MD5" is a code which is unlikely to ever be identical in another file or a changed version of the current one. The code represents the contents of the file but is of course much shorter.
The MD5 codes for files placed into an MSI are listed in the MSI's generated HTML report.
At least version 2.0 of Windows Installer must be installed for this tool to work.