It is "Inno Setup" with the ISCrypt Module, there is a unpacking Plugin for TotalCommander but i dunno if it helps you with the encrypted Files.
http://www.jrsoftware.org/isdl.php
http://www.totalcmd.net/plugring/InnoSetupAddon.html
Other unpacking Project:
http://innounp.sourceforge.net/
"Install Explorer" Plugin for the "FAR Manager" that should unpack it too:
ftp://ftp.sac.sk/pub/sac/utilfile/instexpl.rar
Äh, and the ISCrypt Module is Open Source and just a couple of Lines long, so it shouldn't be that hard to figure out if its possible to bruteforce this before the Sun is burning out
