UPX is a Portable Executable Compressor or “Exe Packer” that operates from a command line or drag and drop. This Free Executable Compression Utility allows you to compress executable files with an excellent compression ratio while still retaining fast decompression (compresses better than zip or gzip). UPX uses very little system resources to accomplish it’s task and you can list, test and unpack your executables using the same tool. Additionally, a checksum of both the compressed and uncompressed file is maintained internally.
UPX Executable Compressor in action
Note that if you just want to compress an executable, just drag and drop your exe file onto upx.exe. Advanced usage requires the use of commands and options outlined in upx.doc.
UPX Extracted Size: 480KB
UPX Website: http://upx.sourceforge.net
UPX License: Open Source
UPX Download: You can get this EXE Packer HERE