The latest ver of UPX (Ultimate Packer for eXecutables) is v2.03
and the latest GUI interface available FREE for it is here:
http://www.compexpsoft.com/advshell.html

<quote>
"Advanced Shell is a friendly front-end Windows shell for UPX
version 2.03. UPX [...] is the best executable file compressor around,
typically reducing the size of executables and DLLs by 50% to 70%.
This reduction in size reduces disk space requirements, network load
times, download times, storage costs, and make distribution much
easier.

The front-end interface for UPX is not the easiest to work with, so
we designed Advanced Shell as a friendly and efficient front end that
runs under all versions of Windows. Advanced Shell allows you to have
easy control of all the UPX features without needing knowledge of the
UPX commands and options. Advanced Shell makes your UPX work more
effective and comfortable.

Programs and libraries compressed by UPX are completely self-contained
and run exactly as they did before compression, with no runtime or
memory penalty for most supported formats. UPX supports a wide range
of executable formats, including Windows 95/98/ME/NT/2000/XP
programs and DLLs, DOS programs, and Linux executables."
</quote>