In the past, the only real way to get a Windows machine back to its original out-of-box state has been the tedious process of formatting and reinstalling. Windows 8 promises to make the process much simpler, offering a complete reset option as well as the ability to reinstall Windows while maintaining your data.
Microsoft outlines how the two features will work in a post on its Building Windows 8 blog. If you choose a complete reset, you'll be given the choice of whether you want to "thoroughly" erase data -- a slow process -- or if you're happy to just perform a basic erase:
This is a handy development, but the option I really like the sound of is refreshing the install while keeping your data and settings. Definitely useful if you've experienced a malware issue or just want to blast out older software. The refresh option will automatically restore newer Metro-style apps (those written specifically for Windows 8), but older apps will need to be reinstalled manually. Hit the post for more details of how it will work when Windows 8 eventually appears (perhaps this year, but nothing is yet set in concrete).
Refresh and reset your PC [Building Windows 8]