PECompact

PECompact is a utility of the genre known as "executable packers" or "executable compressors". Executable packers compress executable modules so that their physical size is considerably smaller. At runtime, compressed modules (executables) are rapidly decompressed and reconstructed in memory.

In fact, decompression and reconstruction is so rapid that load time usually improves since the time saved by reading fewer bytes from the disk or network often exceeds the time spent reconstructing and decompressing in memory.

And the compression ratio? It's better than any general purpose compression software like ZIP, RAR, or 7-ZIP. This is because PECompact is optimized for a specific type of file format: executables.