Though I am sure this is not what you want to hear, if you forgot the administrator password and don't have another administrator account, you won't be able to reset the password. Since there are no other user accounts on the computer, you will not be able to log on to Windows and will need to re-install Windows.
Have you tried all the password possibilities that you can think of? If someone else created the password, check with them to see if they remember it.
i recently did a system restore on my computer. once it was done it re-installed all the factory programs, once all that was done i was able to use my computer perfectly. when i was finished using the computer i shut it down but when i turned i back on the next day it said that the administrator account has been disabled and I'm not able to access my computer because i don't know the password that it is asking me for.