I use Universal Extractor from LegRoom.net pretty often to tear open setup packages of software.
There are lots of install packages that use 7-ZIP formats, quite a few MSI based installers, primarily from Microsoft, but more time than not, many packages are wrapped by Inno Setup.
Universal Extractor hasn’t been updated for quite some time. And in many cases, if you stick with the default package, you will encounter a Inno packed set that it can’t open up.
Luckily, because there are so many supported formats Jared Breland has packed in there, it generally is pretty easy to figure out what component you need to update, check that source location, and swap the older one out with a newer one.
Accordingly, I keep a very close eye over at innounp so I can always have the newest version of an Inno unpacker tucked into my Universal Extractor.
Current version of Innounp is 0.37 supporting Inno Setup versions 2.0.8 to 5.5.0.