An excellent program which I have used for making my own autorun.exe programs is Autoplay Media Studio Pro from IndigRose
http://www.indigorose.com/ams/index.php
This is a quite expensive program but you can find bargain prices....if you know what I mean
You can use CabPack
http://home.t-online.de/home/lars.hederer/english.htm
to edit .cab files but you have to save as new cabs. This program will not edit Installsheild cabs though.
For Installsheild cabs You need the ICOMP cab editor which can be found here
http://cdmediaworld.com/hardware/cdrom/files.shtml. I have used this program many times to insert the cracked game executable into the setup cab and make a cracked setup and it will also extract files. ICOMP does not have a GUI, it command line based.