Does anybody know of any software which will allow me to compress an ISO. file?
If you are just aiming to compress it for moving, then 7-Zip or another decent file compressor is what you're aiming for, just don't expect them to do too much as often the contents of ISOs are already compressed (plus it can take a REALLY long time to try and compress huge ISOs for little to no gain)
Any compression software will compress an iso file.
However, I suspect you want something more... like compress the iso file bust have it still be an iso compatible image?
For that, I don't that that is doable.
I think what would be blank space (and thus zeroing would be a win) on a HD image, but I bet a CD has none, and probably just automatically files the empty space at the end of files with 0 anyways.
So no, 7zip is probably your best bet if you want to save space.
MagicISO supports Universal Image Format (UIF) which supports compression and encryption. Although compressed, the image is still mountable.