Is this an upgrade only or can it be used for new builds? I am building a new system and wondering if you have to have a previous version of windows already installed or can it be installed on a newly formatted hard drive?
This is only the upgrade option. Not a OEM or retail full license, you need an xp, vista, or 7 license already to upgrade from this key. Microsoft has said that the full version will cost more and when the special offer expires AKA January 2013 it will cost even more.
As long as you have Windows XP or later on your computer, you may use this to wipe your drive and do a clean install. If you are building a new PC and happen to have Windows 7 or earlier, you can install that one and then use this upgrade to create a clean install of Windows 8. If you do not have any of that, you are not supposed to be able to use this as it is only an upgrade. The full version OEM is $20 more from newegg.com right now.
If you look at this product: Microsoft Windows 8 Pro Pack (Win 8 to Win 8 Pro Upgrade) it has a little link if you want to get an upgrade license. If you click that link, it takes you to this product being discussed. So based on that, this is an upgrade only license. I so hate when they are not clear.
That's a gimmick of Amazon to entice you to buy it since MS have said that the Pro upgrade disk is $60 and the download-only upgrade is $40. The OEM/System Builder versión will be $100 for the Home versión and $199 for the Pro version
This is definitely just an upgrade disc but like the win7 upgrade disc you can use the disc as a full upgrade but when it comes time to enter the key code it will deny you and then you'll have 30 days to get the proper code.
The code from the upgrade disc only works as an upgrade code so after a full install it won't work. You should just buy the "System builder" version which is for people starting from scratch and have no OS previously installed. Hope that helps. :)