Well i got A windows 8 professional upgrade and im trying to load it onto a pc that im building from scratch and was wondering if it would work if i downloaded A trial version or evaluation copy of windows 8 and loaded it onto a USB then use the upgrade from there or would i have to buy a full copy of it before i could use the upgrade i got the upgrade for $15 and this is a budget build so if i could save that $100 dollars that it would cost to Buy a system builder that would be great