Now I have the ISO file but I don't want to burn it into DVD so I wonder if there is a way to install Windows 8 right from hard disk ? (do a clean installation from DOS not from any Windows system)
There are two main solutions to install Windows 8 without any optical media (typically using a 4Gb+ USB flash drive).
1. The "Upgrade Assistant" official (promoted) one
If you are already using a previous version of Windows, you can launch the Windows 8 Upgrade Assistant which, among other things, "provides the option to buy, download, and install Windows 8". You can download the ISO file or create a bootable flash drive from this wizard. If you need the ISO file or if you prefer to use this official solution, I recommend the excellent How To Clean Install Windows 8 Pro Upgrade step-by-step tutorial.
By the way, since I bought Windows 8 online, I didn't receive any DVD or even any link to download an ISO, so this first solution is the only one I came up with to download the file and proceed to the installation...
2. The "Windows 7 USB/DVD download tool" official-but-not-really-promoted one
This solution requires you to own the ISO file already (cf. solution #1). Actually The Windows 7 USB/DVD download tool won't download anything, but it will help you to get your flash drive ready for the installation.
Once again, there are some nice and clear step-by-step tutorials over the Web, like How To Install Windows 8 From a USB Device.
Also you might want to know about an interesting third alternative found on Superuser that will spare you a DVD and a flash drive:
3. Install from a partition
Start by creating a 8GB NTFS partition on your hard drive. Then
Bootable USB memory stick (plenty of detailed instructions online as to how to create it) is the only non-DVD local option. I don't believe it's possible to install it from an ISO just on a partition on the local hard drive.
It is possible to install from a Network Share but this of course involves a second machine and is more complicated.