I have posted this question on a Mac forum, but I got no reply. Because I don't want to keep installing my guest OSes each time I reformat my Mac, I have been trying to backup my Parallels VMs to DVD. I have successfully compressed my Linux VMs to fit on DVD, but I'm having troubles with Windows. Its "hdd" file, it was originall 10.76 GB but I was able to get it down to 8.91 GB (too big for both Dual layer and Single layer DVDs), with Parallels Compressor. Since converting sparsed images and compressing them into gzip files only lowers them to 5.44 GB (still too big for single layer, but more than small enough to fit on Dual layer DVDs), How can I compress it even further to make the Windows VM fit onto a single layer DVD? If I must, I will get an external hard drive or some double layer DVDs, but for now I want to save money and stick with my DVD-RW discs.