Need help bootcamping Windows 8

For the consumer preview, I burned the ISO to disc, and went through the motions of installing it on my 27" iMac. Since then, I had deleted it thinking I wouldn't need it to upgrade to 8 proper. I still have that disc, but now, it wont install. It errors about 30% through the install. When I bought Windows 8, I got it via download from MS.com During that process, they asked if you wanted to make a DVD of it, or make a USB drive of it. I chose USB (I was on my old netbook at the time.)

Now when I go to bootcamp in OSX MountainLion, it only gives me the option to install Windows from DVD. The thumb drive also doesn't even show up on list of C: D: E: etc. drives when I use the consumer preview DVD to get to that stage.

I spent a lot of money. I bought 8 using my live.com email, my Xbox account, you know, and I wonder if MS will let me redownload it and make the DVD this time. Or if there is a way to extract the data from the thumb drive and create the DVD from it.

I thought you could only download the Windows 8 upgrade. Don't you have to buy the OEM version if you want a completely fresh install?