*WARNING* disregard my earlier statement about 70 dollars for a full copy. That best buy rep was full of it. I just finished installing windows 8 on my desktop and it wouldn't take the serial code. There is apparently two different packages for the upgrades. I just found with customer service in best buy for over 40 minutes because they weren't going to let me return it because it was opened. I eventually convinced them to let me exchange for the OEM edition that they don't carry in store and is actually hidden from their search menus! So if you want a full version, here is the link: Windows 8 Professional 64-Bit System Builder (OEM) - Windows
This is more normal priced at 140.