All of your operations are inside the vm, to the virtual disk, so there is no risk destroying your real hard disk. You can click those buttons.
If you want to give it a try first, we have a pre-installed VHD file for Fedora 13, that you can use to run as a virtual machine, or boot your real computer, truly decompile an OS as simple as a file
. This vhd is a real appliance, as well as virtual appliance. Download http://www.vmlite.com/appliances/fedora-13-readme.html
Ubuntu 10.04 and LinuxMint 9 VHDs are also available.