Clone CD does not compress images - as far as i am aware of, it makes an ISO image, there is no specification in the ISO9660 that calls for compression. (edit: according to one site, CloneCD does not make valid ISO images)
If you compress the ISO image, it will not be readable in cloneCD. I am not aware of any programs which offer ISO compression. Why? It would not be an ISO image then, it would be an ISO in a compressed format, such as a zipped file. If you are aware of any program which offer on the fly decompresion of a compressed image, drop a link.
Otherwise you would either have to use an external compression app. such as WinRAR, WinACE, Gzip, or Bzip. which would require decompression when you want to use the ISO image again.
You could make an ISO image of the CD, then compress it, this would permit you to copy that compressed file to a cd for back up purposes. I have many operating system which i have grouped together in bz2 format, and i store them on a CD. This way i am able to keep several backup images on a single CD.
Did find something that might be interesting for some, wont work for CloneCD, not sure if the project is even still alive. Most likely will only run under a *nix OS. But may work under MS Windows via Cygwin
- Iso9660-compr This project aims to provide a transparent compression scheme for ISO9660 (the format used on CDs), to be able to store larger amounts of data on a CD, providing the user with the illusion of a larger CD, instead of a CD containing many compressed files.
- Alittle more searching revealed these,
- VaporCD (FREEWARE)
Can create a copy of a CD on your hard disk and mount it as if it were the real CD. Support for mounting CD-ROM ISO images. VaporCD works with Windows NT 4.0 or Windows 2000- Paragon CD-ROM Emulator 2.5 Personal Version (SHAREWARE)
Virtual CD-ROM machine creates virtual CD which is up to 100x faster, Mode CDsare stored as compressed images on the hard drive. Paragon CD-ROM Emulator - creates compressed compact-disk images on the hard disk and emulates physical CDROM devices which has hard disk performance.