I just got a new Mac, and everything went fine (I've owned like 6 different macs in my lifetime.) At one point however, I simply wanted to update my XCode app.. so I opened the App Store and clicked on updates, clicked on the update button, but the App Store is requiring me to sign in, but it's asking me to sign in with a different email address (ok I remember I once used a laptop of a coworker a couple of jobs ago and I had to do some updates. I have no idea how this is linked to my laptop now.)
Anyways, I have no idea how to change the apple ID here!
To make things even weirder, if I go to Store menu button, it actually shows my proper account:
So I'm left really confused now.. any ideas?