UPX4PPC is a free application that allows you to compress & optimize EXE/DLL files for softwares installed on your Windows Mobile 2003 and 5.0 based Pocket PC devices.

UPX is not like Zip or Rar formats where you need tools such as WinZip or WinRar for compression as well as decompression. In the case of UPX, it is just a compressor. Decompressors are always embedded into a UPX compressed executable file. That means you do not need any decompressor to run the compressed executable file