Reinstalling Windows 8 with the existing product key

I recently purchased an ASUS laptop with Windows 8 installed. The hard disk capacity is 750 GB. I checked the C drive and could see that they have used almost 40/50 GB for installing Windows 8, including all the graphics drivers and other drivers.

I would like to format my machine and reinstall Windows 8 from scratch. I don't want to use the recovery drive or any other means. Is it possible to install only Windows 8 with the existing product key?

The rest of the software or drivers for my computer will be installed manually.

Get a clean Windows 8 DVD (MSDN/Technet) or remove the ei.cfg from your current DVD. When you now install Windows 8, the setup will use the Key which is embedded to the UEFI.