I'm afraid you're going to be disappointed. The Terms and Conditions make it clear this is only for upgrading a machine that already has Windows installed on it:

"Each upgrade license applies to only one PC and you can install the upgrade only on PCs that have a valid base license and one of the following operating systems: Windows 7, Windows Vista, or Windows XP (SP3)."

http://windows.microsoft.com/en-US/windows-8/terms-condition...

During the upgrade process, you have the option of reformatting the hard drive and doing a "clean install", but it must be on the same disk that already has Windows installed on it.

http://answers.microsoft.com/en-us/windows/forum/windows_8-w...