The Cabinet data type must be used in the Cabinet column of the Media table.

If the cabinet name is preceded by the number sign, the cabinet is stored as a data stream inside the package. The character string which follows the # is an Identifier for this data stream. Note that if the cabinet is stored as a data stream, the name of a cabinet is case-sensitive.

If the cabinet name is not preceded by the number sign #, the cabinet is stored in a separate file located at the root of the source tree specified by the Directory Table. The cabinet file must use the short file name syntax consisting of an eight character name, a period, and a three character extension. The Cabinet data type cannot use the short|longname syntax for file names. If the cabinet file is stored as a separate file, the name of the cabinet file is not case-sensitive.

To conserve disk space, the installer removes any cabinets embedded in the .msi file before caching the installation package on the user's computer.

See Including a Cabinet File in an Installation.