I created a Windows To Go flash drive using 64-bit Windows 8.1. It boots and works perfectly except that I cannot activate it with the license key I got when I paid for Windows 8 last summer (I bought the digital download, ordered the optional disc, and carefully recorded the license key Microsoft e-mailed me). 

I noticed that the "build" of the Windows To Go flash drive states "Windows 8 PRO," not Windows 8 or 8.1. Did I screw up and not install the right version of Windows to the drive? Is Windows To Go only for the PRO version of Windows 8 and not the regular version? I only worked on this as an experiment to see if I could boot Windows 8 on our work PC's (which are sadly still running XP), and I am so close! Where did I go wrong?

Windows 8 PRO is Enterprise Edition? Official Windows to go only with Windows 8/8.1 Enterprise Edition. However, if you have no Enterprise Edition, you can try Aomei Partition Assistant and its new function "windows to go creator"

http://www.disk-partition.com/features/windows-to-go-creator.html

cheers!

You can try WinToUSB, it is the first third-party software released to create Windows To Go drive.

Very professional and easy to use!!!!