Can't reboot to change password because I need the password to reboot.

(all my questions are linked...one after the other) So I asked another question yesterday, and I thought it would finally be the answer to this whole problem but seems I have another problem. These are the great instructions I was following:

http://www.psychocats.net/ubuntu/resetpassword

Until...

I tried to access the screen to reboot by pressing SHIFT while the computer is booting, and I didn't get any results..nothing I tried it aout 5 times.

I read that you can also press ESC while the computer is booting, and result was I just got really fast text in black and white pass before my eyes and then....back to the login screen.

I also read that I can type "sudo reboot" into the Terminal and I did that however when I did it asks for a password...which is my problem so it doesn't help.

I have no idea what I can do..feels like a dead end....if anyone has an idea how I can finally change my password without needing a password!!!...please it is much appreciated Thank you.

Every question I ask I get an answer that is so close..yet so far (-_-) help....