Most option will allow you to choose an alternate set of credentials if an access denied error occurs.
NOTE: This dialog allows you to save your credentials to the registry for later use. The user and domain fields are plaintext and the password is encrypted. Use this option with caution, while the encryption algorithym obfuscates the password very well, no guarantees are given. It is only offered for convieninence.
This is a typical credentials section of the registry.
Username=administrator
Domain=domain
pwdEncrypted=▒QÇeAAßY