a bit OT, sorry.
I've written two perl scripts that create 'sparse' iso file. Using them, you can unpack .iso, keep the files, generated sparse iso and offsets file, and finally delete original .iso.
In short, now you can unpack all .iso files and later re-create them.
sparse file is mostly hollow, it can be compressed to several hundred Kb.
You might not gain any extra hdd space with just single iso, but its more convenient to access files.
Greets.
