the local "administrator" account is disabled by default with Windows 7. It is possible to turn it on by searching for Administrative Tools, then using Computer Management, Users
although it's turned off as a security feature. If you enable it, set a STRONG password on it.
Not sure if this answers your question or not but thought i'd put in my 2 pence worth
While this is true, most users don't enable this account, thus the original answer given. The original account used to set up Win 7 is an administrator account and is what most will see when attempting to boot into Safe Mode. If the Administrator has been enabled, per spongmonkey's message, it too would be listed.
Still, what problem are you trying to solve? Are you locked out of your own system?