To access your Simplify3D account, you can login at cloud.simplify3d.com. If the user name/password are forgotten, you can simply go to cloud.simplify3d.com/account/username/forgot to get your username using the email address, then to cloud.simplify3d.com/account/password/forgot to reset the password associated with that email. This will then gain you access to the account online, from which you should be able to remove any Simplify3D installations that may be active and download Simplify3D onto whatever computer you need.