How do I clean install Windows 8 without an Installation Disk?
Why do you want to format the HDD ? you'll remove recovery partition too. Better use windows reset to rest-to-factory.
To reset your PC
Swipe in from the right edge of the screen, tap Settings, and then tap Change PC settings. (If you're using a mouse, point to the upper-right corner of the screen, move the mouse pointer down, click Settings, and then click Change PC settings.)
Under PC settings, tap or click General.
Under Remove everything and reinstall Windows , tap or click Get started.
Follow the instructions on the screen.