In the past when you bought a new computer, it usually included restore media on CD or DVD. Sometimes it’s called recovery media. This media would be used to reinstall the operating and programs which came with the computer. If Windows got so messed up it couldn’t be used, the user could boot with the CD and bring the computer back to the way it came from the factory.
Any more it’s a rarity to get restore media with new computers. This makes it harder for the user to get the computer back to normal when Windows has a major problem. Some computers have a recovery partition on the main hard drive which acts like recovery media and is accessed usually a special key sequence on booting the computer. It will take a screwed up Windows back to the way it came from the factory.
If the hard drive has a physical defect or the recovery partition is corrupt and won’t run and you don’t have recovery media, then it’s going to take longer to restore back to Windows. Many of the current computers have an option to create restore media from within Windows and I suggest you do that now while your computer is running fine. It’s usually under Start-programs- (under the computer manufacturer name) recovery. Or you can search the internet how to do if for your computer. Sometimes when you set up a new computer during the Windows installation it will encourage you to create restore media and blank DVDs will be needed. If no restore media is created, your last option is to buy them from your manufacturer.