Stuck with x86 Windows 8

So I downloaded the x86 Windows 8 Release Preview previously just to try it out, and I ended up keeping it because it was really good. However, when I upgraded from that, I didn't get any option to for x86 or x64, which is a bummer because I have 8GB of RAM and I don't want it to go to waste.

My question is that is it possible to reinstall Windows 8 as x64 without wasting a license. Moreover, can I install Windows 8 more than one time with the $40 upgrade deal, or is it only for one machine? 2.3GB of RAM is still fine though. :/