I have the same issue. I have an Acer Iconia W511, no external devices connected. During first try I haven't realized that it said "Windows 8.1 Preview" in the store. Half an hour later starting the install on another computer it said "Windows 8.1 Update". Right now after updating some drivers I started the installation again. It seems that it completely re-downloads it from the store. But can I be sure with this or do I need to clear some kind of cache to not get any preview bits anymore?
Update: The last try didn't work as well. And I don't get a blue screen, it just turns black after preapring devices and applying settings, I let it run the whole night yesterday but nothing happened. After turning off and on again Windows tries to repair the update, fails and turns into black screen again. After second turn off and on it reverts to the last installed version.