Need help creating ESO account

Just downloaded the complete version on Steam today. It turns out I actually have some old files on my laptop from the War Chiefs pack I had years ago. While it's nice that I have my French civilization, I think it might be messing with my ESO account creation. When I try to make a new account it gives me the Error101 which means my CD key has already been used. However I just bought the thing on Steam so I don't think someone has taken it. My guess is that the game is still reading the old CD key I used years ago and not the new key I downloaded. Do I have to uninstall and delete my old files to get the new ESO account? There's no way I still have the info needed to recover my old ESO account. I'd like to keep my old save because it's nice to have but I don't want to do that if there's another solution.

Thank you for your help. Looking forward to getting back into the game!