Need help resetting or changing my admin username and password without the installation disc

I accidentally clicked on the check box that is located in system preferences in accounts that says "Allow user to administer this computer" and unchecked it. So the account that I set up the user name and password to is not the administer anymore and I don't know what account is. So now every time I want to make changes to anything and click on the lock button it will not accept my username and password. So how do I reset my username and password for the administer without the installation disc and without losing any files or folders????

Message was edited by: ashkonnor8808