I had a similar question. This link seems to answer it? Looks like you need Windows 7 initially but can then do a 'clean' install.
http://answers.microsoft.com/en-us/...on-a-new/e8826718-2557-4970-897e-dcb4d1bfb712
How to do a clean install:
Step 1: Use the Upgrade Assistant to qualify the PC and pay the $40 (US)
Step 2: When the "Install Windows 8" message appears, select "Install by creating media" to create a bootable USB flash drive or an .iso (a disk image) file.
Step 3: Wait for the Assistant to download the Windows 8 Pro installation package and create the bootable media or .iso file. The flash drive must be have 3GB or more of free space available.
Step 4: Burn the .iso file, if that's the path you chose, to a blank DVD.
Step 5: Use that USB drive or DVD to boot the PC.
Step 6: When you get to the screen in Setup that asks, "Which type of installation do you want?' choose "Custom."
Step 7: Select a disk partition for the OS in the next screen. At this point, you can create a new partition if there's enough space available, or reformat the drive.
Step 8: Continue with the installation of Windows 8 Pro.
You will likely have to do a phone activation after installation is complete.
1. Press Windows key + X then click Run, then type: slui.exe 4
2. Next press the 'ENTER' key
3. Select your 'Country' from the list.
4. Choose the 'Phone Activation' option.
5. Stay on the phone (do not select/press any options) and wait for a person to help you with activation.
6. Explain your problem clearly to the support person.