ExEinfo PE!

PEID is a signature scanner , it can detect most common packers, cryptors and compilers for PE files. It can currently detect more than 600 different signatures in PE files.

Free UPX is an advanced graphical interface for the UPX (Ultimate Packer for eXecutables). It offers easy access to all documented and undocumented UPX parameters without the need for command line usage.

Created by Daniel Pistelli, a freeware suite of tools including a PE editor called CFF Explorer and a process viewer. The PE editor has full support for PE32/64. Special fields description and modification (.NET supported), utilities, rebuilder, hex editor, import adder, signature scanner, signature manager, extension support, scripting, disassembler, dependency walker etc. First PE editor with support for .NET internal structures. Resource Editor (Windows Vista icons supported) capable of handling .NET manifest resources. The suite is available for x86 and x64. »

Graphical GUI incl UPX 3.07 and a scrambler. Support Drag & Drop and context-menu. With many further information. UPX. NO external program required. UPX is a very good execompressor and freeware. With this scrambler you can't unpack the exe with upx any more. With German manual. New: You can choose between external (DOS-Windows) or an internal output, Result after compression. You can choose an external UPX.EXE or the internal. Incl Reduce

Crinkler is an executable file compressor (or rather, a compressing linker) for Windows specifically targeted towards executables with a size of just a few kilobytes. As of 2011, it is the most widely used tool for compressing 4k intros.

pefile is a multi-platform Python module to read and work with Portable Executable (aka PE) files. Most of the information in the PE Header is accessible, as well as all the sections, section's information and data.

WWPack32 - Windows executable files compressor and protector. Compressed exe and dll files run exactly as before!. This program squeezes exe files and protects Win32 applications from cracking.