This one may save someone some time. One of the kid's computers was on windows 7 and I thought it might be nice to try going to 8 as they've put the countdown on windows 7.
I tried the DVD from within Windows 7 and booting the DVD. Booting from the DVD won't let you update and from within Windows it failed after it got to 100%.
I had recently installed an SSD and disabled superfetch and Windows search services. After trying a few other things I re-enabled these and it worked.