Sign in to ** to update application for that account So I somehow grabbed my parents USB thumb drive to install Mountain Lion. Now when I want to upgrade to Mavericks, its asking me to sign into my parents icloud account. 

So I rebooted, did an Internet Recovery, and it installed a clean version of Mountain Lion. It's prompting me again still.

How can I re-associate my Mac Mini to my icloud account?
these are sort of "nuke from orbit" directions; there's likely a less extreme way, but this should work:


shutdown
boot to single-user mode by holding down ⌘ command-s on boot
enter these commands at the console

fsck -fy
mount -uw /
rm /var/db/.AppleSetupDone
shutdown -r now

run through the Setup Assistant creating a new administrator account