It's actually more along the lines of 1.21 gigawatts.
From the associated doc in your link:
"To upgrade to Windows 8.1 from Windows Vista or Windows XP, you'll need to install it from a Windows 8.1 DVD and perform a clean installation. This means you won't be able to keep any files, settings, or programs when you upgrade."
That's definitely not an "in-place" upgrade, which is what the OP wants, I'm guessing. (I know it's what I want.)
Seriously, it seems like this question comes up every few (2-6) months. Can we have the submitters just search the archives before posting? It's not like there's been some sea change in IT world that would preclude the same answers.
Over and over.
Can we just get back to stale tech news already?