If needed, you can reset your Developer Sandbox Account password using the forgot password link: https://sandbox.authorize.net.

You will be asked to provide the answer to the Secret Question which is usually your Pet's Name. If you have not updated your Secret Answer, the default answer is Simon.

For more information about Developer Sandbox Accounts, please check:

http://community.developer.authorize.net/t5/The-Authorize-Net-Developer-Blog/Authorize-Net-Test-Acco...