Forgotten admin password

i have a keyboard problem on my macbook (2009) which is just showing symbols instead of letters so i have an external keyboard set-up. I have forgotten my admin password so i cannot update etc and i have no disk. I have read somewhere that you can boot into single user mode and put in a long list of codes however the windows keyboard i am using will not let me do this.... Any idea how to reset the password, or will downloading the osx again and installing it fix it? Its getting annoying now