You can use a USB stick instead. See the instructions here.
Alternatively, there are ways to install a secondary (dual-boot) OS without any external media, depending on what OS you already have, but they're a bit hairy. The CD/USB method allows you to completely wipe the machine and install afresh. The alternative method only lets you install alongside the old one.
First, you need to make space on your disk. That might meaning shrinking some partitions, or maybe you have one you can just delete. You can't usually do that if you're running from the disk at the time, so you might be stuck at this point already. You may have more luck doing this if you boot the OS in "recovery mode" (Ubuntu has such a thing, but I don't know about SUSE). You'll need at least one primary partition remaining as you can't install anything bootable in the extended partition.
Once you've prepared your disk, you'll need some VM software. I've done this using kvm/qemu in the past, but I think VMWare and maybe VirtualBox should work also. The VM is only a temporary step. If your hareware doesn't support virtualization you'll need VM software with a fall-back emulation mode (the installer will run slowly, but should still work).
You need to create a new VM that boots from your ISO image, and has your real hard drive as it's disk (i.e. not a virtual disk like you would normally use for a VM). You normally need to be running as root user to have access to the bare disk device. It will be called something like
/dev/hda. Use the device without the partition number (i.e. not
You can test if you've got the disks right by configuring it to boot from the hard disk; if it's working it'll try to boot you existing OS inside the VM. Don't let it boot very far though - you should interrupt it before it has time to interfere with anything.
When you've booted your VM, you should see the normal LiveCD boot process. Run the installer and tell it to install alongside the existing OS. Do not let it overwrite any part of your existing OS or else Bad Things will happen very quickly (it's very not good to delete an OS as it's running).
Hopefully the install process will continue exactly as normal, and install everything in the right place. Once it's complete, you can reboot the new OS inside the VM to test it, if you wish. The boot screen should allow you to choose between the old OS and the new. Be sure to choose the new.
Once your happy the new OS installed OK, you can shut down the VM, and reboot the machine. It should come up with the new boot menu and you should be able to choose between the old and new OS.
If you're happy with the new install, you can always delete the old one by reformatting its partitions, and deleting it from your Grub config. You'll probably be stuck with an odd partition table for the life of the machine though.