Hi James, 

Welcome to Box Community.

Because your previous admin registered your Box account with a corporate email address, you will need to enlist your company's IT department to reactivate this user's email address for long enough to receive a password reset email.

With access to your old admin's email, please follow these steps:
1. Go to www.box.com/reset and enter the old admin's login email
2. Click "Reset password"
3. Check the old admin's email for a password reset link

Once you've logged in to the old admin's account, please refer to the instructions in this support article to assign his/her privileges to the new admin.

Feel free to reply back to this message if you need further assistance.