If your PC is relatively new, there should be options on the BIOS screen, the screen that displays right after you turn on the computer and before Windows begins loading. The message is typically at the bottom right side of your screen, and may say something like "F2 BIOS F11 boot options F12 Restore". You want to hit the key that says something about restoring your system or resetting the system. Once you hit that key the system will step you through the process.
Be quick, you won't have much time to hit the key. In fact you may have to start your computer a couple of times before you can read which key to hit.