NOTE: Using UPX 3.08 on Windows 7
The original uncompressed Peerblock.exe file (1,866,864 bytes) works. Installer found at http://www.peerblock.com/
Peerblock.exe still works when compressed with UPX 3.08 using the "--best" or "--lzma" arguments (714,352 bytes and 646,768 bytes respectively).
Yet, when DECOMPRESSED, these files no longer work, although they both are the same size as the original uncompressed executable. The decompressed files are also identical to one another.
If RECOMPRESSED, the resulting files are significantly smaller than the original compressed files and also do not work (697,456 bytes vs. 714,352 bytes for "--best" compression and 632,944 bytes vs. 646,768 bytes for "--lzma" compression).