I believe the following links will answer your questions:
The trick is the order in executing the steps. It appears you may have started at the last step before doing the first two:
deauthorizing the computer in iTunes and
signing OUT of iCloud. That later step will disconnect the computer from your Apple ID. Those two steps affect who Apple thinks the
user is at
Apple's end. The re-formatting only affects who the
computer thinks
you are.Since you have already reformatted and re-installed
Mavericks, you start up iTunes and see if you can DE-authorize the computer. You can also check the iCloud and see if you are still signed in. After performing those two actions, it would be wise to do the re-formatting again, probably with at least the second, 1-pass over writing option in the "Security Options..." button. Better safe than sorry. It's a jungle out there. A stitch in time saves nine. [insert your favorite cliché here]
BTW, if you can't sign IN while in iTunes, you can also DE-
ASSOCIATE the computer (assuming you ever registered it) at this page: <
My Support Profile> at Apple