In addition to using virtual machines, remember that once a virtual machine is installed, you can use 7zip (or any zipping program) to archive the whole folder containing the vm files, so if something screws up on the vm, you can reset by deleting the folder, restore it from the zipped archive, and trying again without having to do the whole installation process over and over. You can make as many of those archives as you want as you get a vm install to different milestones.