Slitherine

Is there any way I can deregister a multiplayer account? My brother registered his on my computer and now he cannot register it on his.

Welcome.

That's not dependent of the computer. Which serial is he using? Your or his?

He logged onto my computer and registered for multiplayer (with my copy of the game). And now I can't switch his name off my copy. He has his own copy on his computer.

Have he registered his copy? If he didn't you could exchange the copies and register his with your name.

If you want to swap serials mail support with both usernames and the serials you want to use for each account. You should never let someone else use your serial as it creates a right mess!