It is possible that you're using a public computer where someone has already made an account. Or your at home and somehow someone else has attempted before you. Or your in one of those places where your ISP gives your address to many different users on their system (which does occur apparently).
Well this is my personal computer that I take everywhere with me. So the only possible thing I could think is that somehow the wireless connection at my brother's house (where I'm at for Christmas) gave his computer and my computer the same ip addresses.
Either way, the the handle I tried to register is Rha Prel.
Yes, your IP is based upon the connection you are using, and not the computer you are connecting from.
If your brother plays SWC, then I advise you to wait until you return home to register again. On the other hand, if you and your brother visit one another frequently and intend to log into SWC from each other's connections, then you may as well just go ahead and register as a multi to allow yourselves to do this.
"May the Grace of Ara go with you, and His Vengeance be wrought upon your enemies."