To date, reinstalling Windows has meant using a local copy -- either something already stored on your PC (and thus at risk of going bad) or something external. Soon, though, it might just be a matter of grabbing it online. On top of changing tablet mode, the latest Windows 10 Insider Preview Build on the Fast ring includes a "download Windows" option when you want to reset your PC. Much like the feature Macs have had for years, you can use your broadband connection to grab a fresh install from the cloud. You don't need a backup partition or a thumb drive to get back in business.
The company stressed that this will wipe your existing apps, and your data should you choose to "remove everything." And remember, this is pre-release software. You'll likely want to wait until there's a polished version before trusting the fate of your PC to the cloud option. When it does arrive, though, it could offer a valuable failsafe if Windows is falling apart and you want a more reliable fix.