When you install or upgrade to Windows 8, or receive a new Windows 8-based PC, one of the first things you should do is create recovery media, providing you with an alternate way to boot the PC and run recovery tools should something go wrong. This process has changed a bit since Windows 7, and now works with both USB-based recovery media as well as disc-based media.
To find the Windows 8 recovery media creator, enter recovery in Start Search and then change the view to Settings. The option you’re looking for is listed as Create a recovery drive in the search results.
The Recovery Media Creator is a desktop-based wizard that will enable you to create recovery media. (Note that you will need a version of this disk that is the same 'bit-ness' as is the version of Windows you're using. So if you are using a 32-bit version of Windows, you will need a 32-bit version of the recovery media as well. If it's 64-bit, you need a 64-bit version of the recovery media. This will happen automatically when you create the media, but it means that you can't necessarily share this media with other PCs, if they're using a different 'bit-ness' version of Windows.)
After clicking Next, you’ll be prompted to connect a USB flash drive, or you’ll see a list of available drives. If you’d rather use optical media (CD-RW or recordable DVD), you can click the link titled Create a system repair disk with a CD or DVD instead. (This was the only option in Windows 7.) Here, I’ll assume you’re using a USB device, since that’s new to Windows 8.
After selecting the drive, click Next. The wizard will warn you that everything on the drive will be deleted as part of the formatting process. Click Create.
The wizard will prepare and format the drive, and then copy over the utilities and other files that make up the recovery environment.
And … that’s it. If your PC isn’t booting properly, you can boot it from the recovery media to access a recovery environment that includes several useful tools.
Note that there are also other ways to access these recovery tools, and that the recovery media, in many ways, is a prudent, “just in case” last resort. If you have Windows 8 Setup media, that can be used to access the recovery tools. (On the Install Now screen, simply click Repair your computer instead.) And if you can actually boot into Windows, just navigate to PC Settings, General, and then Advanced Startup to access the exact same toolset.