Microsoft has revealed two interesting features of the upcoming Windows 8, refresh and reset. Reset will remove all data, apps and settings from a PC, and then reinstall a fresh copy of Windows. Refresh, on the other hand, will simply reinstall Windows, but keep all data, metro apps and "important" settings. Metro apps are the new Metro style applications introduced along with Windows 8. All other desktop applications have to be manually reinstalled. If your PC cannot boot you will still be able to refresh or reset it. Here are some screenshots and a video of what to expect.
Moreover Windows 8 will allow you to create an image of the hard drive before you start using your PC. Therefore at any time you are able to revert all changes you have made and quickly get your system back without having to make a complete reinstall.